diff --git a/fennel/client_tests/test_expr.py b/fennel/client_tests/test_expr.py
index 48470874..fd01f545 100644
--- a/fennel/client_tests/test_expr.py
+++ b/fennel/client_tests/test_expr.py
@@ -1,4 +1,4 @@
-from datetime import datetime, timezone
+from datetime import datetime, timezone, timedelta
 from typing import Optional
 
 import pandas as pd
@@ -47,6 +47,7 @@ class UserInfoFeatures:
     assert response.status_code == requests.codes.OK, response.json()
 
     now = datetime.now(timezone.utc)
+    now_1y = now - timedelta(days=365)
     df = pd.DataFrame(
         {
             "user_id": [1, 2, 3, 4, 5],
@@ -59,7 +60,7 @@ class UserInfoFeatures:
                 datetime(2001, 1, 21, tzinfo=timezone.utc),
             ],
             "country": ["India", "USA", "Africa", "UK", "Chile"],
-            "ts": [now, now, now, now, now],
+            "ts": [now_1y, now_1y, now_1y, now_1y, now_1y],
         }
     )
     response = client.log("fennel_webhook", "UserInfoDataset", df)
@@ -97,3 +98,52 @@ class UserInfoFeatures:
         "Chile",
         pd.NA,
     ]
+
+    if not client.is_integration_client():
+        df = client.query_offline(
+            inputs=[UserInfoFeatures.user_id],
+            outputs=[
+                UserInfoFeatures.name,
+                UserInfoFeatures.age,
+                UserInfoFeatures.country,
+            ],
+            input_dataframe=pd.DataFrame(
+                {
+                    "UserInfoFeatures.user_id": [1, 2, 3, 4, 5, 6],
+                    "timestamp": [
+                        now_1y,
+                        now_1y,
+                        now_1y,
+                        now_1y,
+                        now_1y,
+                        now_1y,
+                    ],
+                }
+            ),
+            timestamp_column="timestamp",
+        )
+        assert df.shape == (6, 4)
+        assert df["UserInfoFeatures.name"].tolist() == [
+            "Ross",
+            "Monica",
+            "Chandler",
+            "Joey",
+            "Rachel",
+            pd.NA,
+        ]
+        assert df["UserInfoFeatures.age"].tolist() == [
+            53,
+            43,
+            33,
+            25,
+            22,
+            pd.NA,
+        ]
+        assert df["UserInfoFeatures.country"].tolist() == [
+            "India",
+            "USA",
+            "Africa",
+            "UK",
+            "Chile",
+            pd.NA,
+        ]
diff --git a/fennel/expr/expr.py b/fennel/expr/expr.py
index 0cddad8d..c713faa5 100644
--- a/fennel/expr/expr.py
+++ b/fennel/expr/expr.py
@@ -7,6 +7,7 @@
 from typing import Any, Callable, Dict, Type, Optional
 import pandas as pd
 
+from fennel._vendor.pydantic import BaseModel  # type: ignore
 from fennel.dtypes.dtypes import FENNEL_STRUCT, FENNEL_STRUCT_SRC_CODE
 from fennel.internal_lib.schema.schema import (
     convert_dtype_to_arrow_type_with_nullable,
@@ -17,6 +18,7 @@
 from fennel_data_lib import assign, type_of, matches
 
 import fennel.gen.schema_pb2 as schema_proto
+import fennel.gen.expr_pb2 as expr_proto
 from fennel.internal_lib.schema import (
     get_datatype,
     cast_col_to_arrow_dtype,
@@ -26,7 +28,9 @@
     is_user_defined_class,
 )
 
-NOW_COL_NAME = "__fennel_ts_col__"
+
+class ExprContext(BaseModel):
+    now_col_name: Optional[str] = None
 
 
 class InvalidExprException(Exception):
@@ -362,6 +366,7 @@ def eval(
         schema: Dict,
         output_dtype: Optional[Type] = None,
         parse=True,
+        context: Optional[ExprContext] = None
     ) -> pd.Series:
         from fennel.expr.serializer import ExprSerializer
 
@@ -412,8 +417,12 @@ def pa_to_pd(pa_data, ret_type, parse=True):
             ret_type = output_dtype
 
         serialized_ret_type = get_datatype(ret_type).SerializeToString()
+        if context is None:
+            serialized_context = expr_proto.ExprContext().SerializeToString()
+        else:
+            serialized_context = expr_proto.ExprContext(**context.dict()).SerializeToString()
         arrow_col = assign(
-            proto_bytes, df_pa, proto_schema, serialized_ret_type
+            proto_bytes, df_pa, proto_schema, serialized_ret_type, serialized_context
         )
         return pa_to_pd(arrow_col, ret_type, parse)
 
diff --git a/fennel/expr/test_expr.py b/fennel/expr/test_expr.py
index 0f7ac409..ce7caf60 100644
--- a/fennel/expr/test_expr.py
+++ b/fennel/expr/test_expr.py
@@ -13,7 +13,6 @@
     TimeUnit,
     from_epoch,
     make_struct,
-    NOW_COL_NAME,
 )
 from fennel.expr.visitor import ExprPrinter, FetchReferences
 from fennel.expr.serializer import ExprSerializer
@@ -1359,23 +1358,17 @@ def test_now():
             df=pd.DataFrame(
                 {
                     "birthdate": [
-                        datetime(2023, 1, 1, tzinfo=timezone.utc),
-                        datetime(2023, 1, 2, tzinfo=timezone.utc),
+                        datetime.now(timezone.utc),
+                        datetime.now(timezone.utc),
                         None,
-                        datetime(2023, 1, 3, tzinfo=timezone.utc),
-                    ],
-                    NOW_COL_NAME: [
-                        datetime(2023, 1, 31, tzinfo=timezone.utc),
-                        datetime(2023, 1, 31, tzinfo=timezone.utc),
-                        datetime(2023, 1, 31, tzinfo=timezone.utc),
-                        datetime(2023, 1, 31, tzinfo=timezone.utc),
+                        datetime.now(timezone.utc),
                     ],
                 }
             ),
-            schema={"birthdate": Optional[datetime], NOW_COL_NAME: datetime},
+            schema={"birthdate": Optional[datetime]},
             display='SINCE(NOW(), col("birthdate"), unit=TimeUnit.DAY)',
             refs={"birthdate"},
-            eval_result=[30, 29, pd.NA, 28],
+            eval_result=[0, 0, pd.NA, 0],
             expected_dtype=Optional[int],
             proto_json=None,
         ),
diff --git a/fennel/gen/expr_pb2.py b/fennel/gen/expr_pb2.py
index a72efdd9..c821a95f 100644
--- a/fennel/gen/expr_pb2.py
+++ b/fennel/gen/expr_pb2.py
@@ -14,7 +14,7 @@
 import fennel.gen.schema_pb2 as schema__pb2
 
 
-DESCRIPTOR = _descriptor_pool.Default().AddSerializedFile(b'\n\nexpr.proto\x12\x11\x66\x65nnel.proto.expr\x1a\x0cschema.proto\"\xe8\x06\n\x04\x45xpr\x12%\n\x03ref\x18\x01 \x01(\x0b\x32\x16.fennel.proto.expr.RefH\x00\x12\x36\n\x0cjson_literal\x18\x02 \x01(\x0b\x32\x1e.fennel.proto.expr.JsonLiteralH\x00\x12)\n\x05unary\x18\x04 \x01(\x0b\x32\x18.fennel.proto.expr.UnaryH\x00\x12\'\n\x04\x63\x61se\x18\x05 \x01(\x0b\x32\x17.fennel.proto.expr.CaseH\x00\x12+\n\x06\x62inary\x18\x06 \x01(\x0b\x32\x19.fennel.proto.expr.BinaryH\x00\x12+\n\x06isnull\x18\x07 \x01(\x0b\x32\x19.fennel.proto.expr.IsNullH\x00\x12/\n\x08\x66illnull\x18\x08 \x01(\x0b\x32\x1b.fennel.proto.expr.FillNullH\x00\x12,\n\x07list_fn\x18\t \x01(\x0b\x32\x19.fennel.proto.expr.ListFnH\x00\x12,\n\x07math_fn\x18\n \x01(\x0b\x32\x19.fennel.proto.expr.MathFnH\x00\x12\x30\n\tstruct_fn\x18\x0b \x01(\x0b\x32\x1b.fennel.proto.expr.StructFnH\x00\x12,\n\x07\x64ict_fn\x18\x0c 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+DESCRIPTOR = _descriptor_pool.Default().AddSerializedFile(b'\n\nexpr.proto\x12\x11\x66\x65nnel.proto.expr\x1a\x0cschema.proto\"9\n\x0b\x45xprContext\x12\x19\n\x0cnow_col_name\x18\x01 \x01(\tH\x00\x88\x01\x01\x42\x0f\n\r_now_col_name\"\xe8\x06\n\x04\x45xpr\x12%\n\x03ref\x18\x01 \x01(\x0b\x32\x16.fennel.proto.expr.RefH\x00\x12\x36\n\x0cjson_literal\x18\x02 \x01(\x0b\x32\x1e.fennel.proto.expr.JsonLiteralH\x00\x12)\n\x05unary\x18\x04 \x01(\x0b\x32\x18.fennel.proto.expr.UnaryH\x00\x12\'\n\x04\x63\x61se\x18\x05 \x01(\x0b\x32\x17.fennel.proto.expr.CaseH\x00\x12+\n\x06\x62inary\x18\x06 \x01(\x0b\x32\x19.fennel.proto.expr.BinaryH\x00\x12+\n\x06isnull\x18\x07 \x01(\x0b\x32\x19.fennel.proto.expr.IsNullH\x00\x12/\n\x08\x66illnull\x18\x08 \x01(\x0b\x32\x1b.fennel.proto.expr.FillNullH\x00\x12,\n\x07list_fn\x18\t \x01(\x0b\x32\x19.fennel.proto.expr.ListFnH\x00\x12,\n\x07math_fn\x18\n \x01(\x0b\x32\x19.fennel.proto.expr.MathFnH\x00\x12\x30\n\tstruct_fn\x18\x0b 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 _globals = globals()
 _builder.BuildMessageAndEnumDescriptors(DESCRIPTOR, _globals)
@@ -23,120 +23,122 @@
   DESCRIPTOR._options = None
   _globals['_MAKESTRUCT_FIELDSENTRY']._options = None
   _globals['_MAKESTRUCT_FIELDSENTRY']._serialized_options = b'8\001'
-  _globals['_UNARYOP']._serialized_start=5321
-  _globals['_UNARYOP']._serialized_end=5348
-  _globals['_BINOP']._serialized_start=5351
-  _globals['_BINOP']._serialized_end=5485
-  _globals['_TIMEUNIT']._serialized_start=5488
-  _globals['_TIMEUNIT']._serialized_end=5619
-  _globals['_EXPR']._serialized_start=48
-  _globals['_EXPR']._serialized_end=920
-  _globals['_NOW']._serialized_start=922
-  _globals['_NOW']._serialized_end=927
-  _globals['_VAR']._serialized_start=929
-  _globals['_VAR']._serialized_end=948
-  _globals['_FROMEPOCH']._serialized_start=950
-  _globals['_FROMEPOCH']._serialized_end=1047
-  _globals['_DATETIMELITERAL']._serialized_start=1050
-  _globals['_DATETIMELITERAL']._serialized_end=1223
-  _globals['_MAKESTRUCT']._serialized_start=1226
-  _globals['_MAKESTRUCT']._serialized_end=1423
-  _globals['_MAKESTRUCT_FIELDSENTRY']._serialized_start=1353
-  _globals['_MAKESTRUCT_FIELDSENTRY']._serialized_end=1423
-  _globals['_JSONLITERAL']._serialized_start=1425
-  _globals['_JSONLITERAL']._serialized_end=1501
-  _globals['_REF']._serialized_start=1503
-  _globals['_REF']._serialized_end=1522
-  _globals['_UNARY']._serialized_start=1524
-  _globals['_UNARY']._serialized_end=1613
-  _globals['_BINARY']._serialized_start=1615
-  _globals['_BINARY']._serialized_end=1740
-  _globals['_CASE']._serialized_start=1742
-  _globals['_CASE']._serialized_end=1840
-  _globals['_WHENTHEN']._serialized_start=1842
-  _globals['_WHENTHEN']._serialized_end=1930
-  _globals['_ISNULL']._serialized_start=1932
-  _globals['_ISNULL']._serialized_end=1982
-  _globals['_FILLNULL']._serialized_start=1984
-  _globals['_FILLNULL']._serialized_end=2075
-  _globals['_LISTOP']._serialized_start=2078
-  _globals['_LISTOP']._serialized_end=2625
-  _globals['_LISTFILTER']._serialized_start=2627
-  _globals['_LISTFILTER']._serialized_end=2696
-  _globals['_LISTMAP']._serialized_start=2698
-  _globals['_LISTMAP']._serialized_end=2763
-  _globals['_LISTSUM']._serialized_start=2765
-  _globals['_LISTSUM']._serialized_end=2774
-  _globals['_LISTMIN']._serialized_start=2776
-  _globals['_LISTMIN']._serialized_end=2785
-  _globals['_LISTMEAN']._serialized_start=2787
-  _globals['_LISTMEAN']._serialized_end=2797
-  _globals['_LISTMAX']._serialized_start=2799
-  _globals['_LISTMAX']._serialized_end=2808
-  _globals['_LISTALL']._serialized_start=2810
-  _globals['_LISTALL']._serialized_end=2819
-  _globals['_LISTANY']._serialized_start=2821
-  _globals['_LISTANY']._serialized_end=2830
-  _globals['_LEN']._serialized_start=2832
-  _globals['_LEN']._serialized_end=2837
-  _globals['_HASNULL']._serialized_start=2839
-  _globals['_HASNULL']._serialized_end=2848
-  _globals['_CONTAINS']._serialized_start=2850
-  _globals['_CONTAINS']._serialized_end=2902
-  _globals['_LISTFN']._serialized_start=2904
-  _globals['_LISTFN']._serialized_end=2990
-  _globals['_MATHOP']._serialized_start=2993
-  _globals['_MATHOP']._serialized_end=3178
-  _globals['_ROUND']._serialized_start=3180
-  _globals['_ROUND']._serialized_end=3206
-  _globals['_ABS']._serialized_start=3208
-  _globals['_ABS']._serialized_end=3213
-  _globals['_CEIL']._serialized_start=3215
-  _globals['_CEIL']._serialized_end=3221
-  _globals['_FLOOR']._serialized_start=3223
-  _globals['_FLOOR']._serialized_end=3230
-  _globals['_MATHFN']._serialized_start=3232
-  _globals['_MATHFN']._serialized_end=3321
-  _globals['_STRUCTOP']._serialized_start=3323
-  _globals['_STRUCTOP']._serialized_end=3361
-  _globals['_STRUCTFN']._serialized_start=3363
-  _globals['_STRUCTFN']._serialized_end=3455
-  _globals['_DICTGET']._serialized_start=3457
-  _globals['_DICTGET']._serialized_end=3554
-  _globals['_DICTOP']._serialized_start=3557
-  _globals['_DICTOP']._serialized_end=3707
-  _globals['_DICTFN']._serialized_start=3709
-  _globals['_DICTFN']._serialized_end=3795
-  _globals['_STRINGOP']._serialized_start=3798
-  _globals['_STRINGOP']._serialized_end=4251
-  _globals['_TIMEZONE']._serialized_start=4253
-  _globals['_TIMEZONE']._serialized_end=4281
-  _globals['_JSONDECODE']._serialized_start=4283
-  _globals['_JSONDECODE']._serialized_end=4341
-  _globals['_STRPTIME']._serialized_start=4343
-  _globals['_STRPTIME']._serialized_end=4416
-  _globals['_TOLOWER']._serialized_start=4418
-  _globals['_TOLOWER']._serialized_end=4427
-  _globals['_TOUPPER']._serialized_start=4429
-  _globals['_TOUPPER']._serialized_end=4438
-  _globals['_STARTSWITH']._serialized_start=4440
-  _globals['_STARTSWITH']._serialized_end=4490
-  _globals['_ENDSWITH']._serialized_start=4492
-  _globals['_ENDSWITH']._serialized_end=4540
-  _globals['_CONCAT']._serialized_start=4542
-  _globals['_CONCAT']._serialized_end=4590
-  _globals['_STRINGFN']._serialized_start=4592
-  _globals['_STRINGFN']._serialized_end=4684
-  _globals['_DATETIMEFN']._serialized_start=4686
-  _globals['_DATETIMEFN']._serialized_end=4784
-  _globals['_DATETIMEOP']._serialized_start=4787
-  _globals['_DATETIMEOP']._serialized_end=4997
-  _globals['_SINCE']._serialized_start=4999
-  _globals['_SINCE']._serialized_end=5089
-  _globals['_SINCEEPOCH']._serialized_start=5091
-  _globals['_SINCEEPOCH']._serialized_end=5146
-  _globals['_STRFTIME']._serialized_start=5148
-  _globals['_STRFTIME']._serialized_end=5221
-  _globals['_PART']._serialized_start=5223
-  _globals['_PART']._serialized_end=5319
+  _globals['_UNARYOP']._serialized_start=5380
+  _globals['_UNARYOP']._serialized_end=5407
+  _globals['_BINOP']._serialized_start=5410
+  _globals['_BINOP']._serialized_end=5544
+  _globals['_TIMEUNIT']._serialized_start=5547
+  _globals['_TIMEUNIT']._serialized_end=5678
+  _globals['_EXPRCONTEXT']._serialized_start=47
+  _globals['_EXPRCONTEXT']._serialized_end=104
+  _globals['_EXPR']._serialized_start=107
+  _globals['_EXPR']._serialized_end=979
+  _globals['_NOW']._serialized_start=981
+  _globals['_NOW']._serialized_end=986
+  _globals['_VAR']._serialized_start=988
+  _globals['_VAR']._serialized_end=1007
+  _globals['_FROMEPOCH']._serialized_start=1009
+  _globals['_FROMEPOCH']._serialized_end=1106
+  _globals['_DATETIMELITERAL']._serialized_start=1109
+  _globals['_DATETIMELITERAL']._serialized_end=1282
+  _globals['_MAKESTRUCT']._serialized_start=1285
+  _globals['_MAKESTRUCT']._serialized_end=1482
+  _globals['_MAKESTRUCT_FIELDSENTRY']._serialized_start=1412
+  _globals['_MAKESTRUCT_FIELDSENTRY']._serialized_end=1482
+  _globals['_JSONLITERAL']._serialized_start=1484
+  _globals['_JSONLITERAL']._serialized_end=1560
+  _globals['_REF']._serialized_start=1562
+  _globals['_REF']._serialized_end=1581
+  _globals['_UNARY']._serialized_start=1583
+  _globals['_UNARY']._serialized_end=1672
+  _globals['_BINARY']._serialized_start=1674
+  _globals['_BINARY']._serialized_end=1799
+  _globals['_CASE']._serialized_start=1801
+  _globals['_CASE']._serialized_end=1899
+  _globals['_WHENTHEN']._serialized_start=1901
+  _globals['_WHENTHEN']._serialized_end=1989
+  _globals['_ISNULL']._serialized_start=1991
+  _globals['_ISNULL']._serialized_end=2041
+  _globals['_FILLNULL']._serialized_start=2043
+  _globals['_FILLNULL']._serialized_end=2134
+  _globals['_LISTOP']._serialized_start=2137
+  _globals['_LISTOP']._serialized_end=2684
+  _globals['_LISTFILTER']._serialized_start=2686
+  _globals['_LISTFILTER']._serialized_end=2755
+  _globals['_LISTMAP']._serialized_start=2757
+  _globals['_LISTMAP']._serialized_end=2822
+  _globals['_LISTSUM']._serialized_start=2824
+  _globals['_LISTSUM']._serialized_end=2833
+  _globals['_LISTMIN']._serialized_start=2835
+  _globals['_LISTMIN']._serialized_end=2844
+  _globals['_LISTMEAN']._serialized_start=2846
+  _globals['_LISTMEAN']._serialized_end=2856
+  _globals['_LISTMAX']._serialized_start=2858
+  _globals['_LISTMAX']._serialized_end=2867
+  _globals['_LISTALL']._serialized_start=2869
+  _globals['_LISTALL']._serialized_end=2878
+  _globals['_LISTANY']._serialized_start=2880
+  _globals['_LISTANY']._serialized_end=2889
+  _globals['_LEN']._serialized_start=2891
+  _globals['_LEN']._serialized_end=2896
+  _globals['_HASNULL']._serialized_start=2898
+  _globals['_HASNULL']._serialized_end=2907
+  _globals['_CONTAINS']._serialized_start=2909
+  _globals['_CONTAINS']._serialized_end=2961
+  _globals['_LISTFN']._serialized_start=2963
+  _globals['_LISTFN']._serialized_end=3049
+  _globals['_MATHOP']._serialized_start=3052
+  _globals['_MATHOP']._serialized_end=3237
+  _globals['_ROUND']._serialized_start=3239
+  _globals['_ROUND']._serialized_end=3265
+  _globals['_ABS']._serialized_start=3267
+  _globals['_ABS']._serialized_end=3272
+  _globals['_CEIL']._serialized_start=3274
+  _globals['_CEIL']._serialized_end=3280
+  _globals['_FLOOR']._serialized_start=3282
+  _globals['_FLOOR']._serialized_end=3289
+  _globals['_MATHFN']._serialized_start=3291
+  _globals['_MATHFN']._serialized_end=3380
+  _globals['_STRUCTOP']._serialized_start=3382
+  _globals['_STRUCTOP']._serialized_end=3420
+  _globals['_STRUCTFN']._serialized_start=3422
+  _globals['_STRUCTFN']._serialized_end=3514
+  _globals['_DICTGET']._serialized_start=3516
+  _globals['_DICTGET']._serialized_end=3613
+  _globals['_DICTOP']._serialized_start=3616
+  _globals['_DICTOP']._serialized_end=3766
+  _globals['_DICTFN']._serialized_start=3768
+  _globals['_DICTFN']._serialized_end=3854
+  _globals['_STRINGOP']._serialized_start=3857
+  _globals['_STRINGOP']._serialized_end=4310
+  _globals['_TIMEZONE']._serialized_start=4312
+  _globals['_TIMEZONE']._serialized_end=4340
+  _globals['_JSONDECODE']._serialized_start=4342
+  _globals['_JSONDECODE']._serialized_end=4400
+  _globals['_STRPTIME']._serialized_start=4402
+  _globals['_STRPTIME']._serialized_end=4475
+  _globals['_TOLOWER']._serialized_start=4477
+  _globals['_TOLOWER']._serialized_end=4486
+  _globals['_TOUPPER']._serialized_start=4488
+  _globals['_TOUPPER']._serialized_end=4497
+  _globals['_STARTSWITH']._serialized_start=4499
+  _globals['_STARTSWITH']._serialized_end=4549
+  _globals['_ENDSWITH']._serialized_start=4551
+  _globals['_ENDSWITH']._serialized_end=4599
+  _globals['_CONCAT']._serialized_start=4601
+  _globals['_CONCAT']._serialized_end=4649
+  _globals['_STRINGFN']._serialized_start=4651
+  _globals['_STRINGFN']._serialized_end=4743
+  _globals['_DATETIMEFN']._serialized_start=4745
+  _globals['_DATETIMEFN']._serialized_end=4843
+  _globals['_DATETIMEOP']._serialized_start=4846
+  _globals['_DATETIMEOP']._serialized_end=5056
+  _globals['_SINCE']._serialized_start=5058
+  _globals['_SINCE']._serialized_end=5148
+  _globals['_SINCEEPOCH']._serialized_start=5150
+  _globals['_SINCEEPOCH']._serialized_end=5205
+  _globals['_STRFTIME']._serialized_start=5207
+  _globals['_STRFTIME']._serialized_end=5280
+  _globals['_PART']._serialized_start=5282
+  _globals['_PART']._serialized_end=5378
 # @@protoc_insertion_point(module_scope)
diff --git a/fennel/gen/expr_pb2.pyi b/fennel/gen/expr_pb2.pyi
index d949dcdb..3757436e 100644
--- a/fennel/gen/expr_pb2.pyi
+++ b/fennel/gen/expr_pb2.pyi
@@ -110,6 +110,23 @@ MICROSECOND: TimeUnit.ValueType  # 8
 MILLISECOND: TimeUnit.ValueType  # 9
 global___TimeUnit = TimeUnit
 
+@typing_extensions.final
+class ExprContext(google.protobuf.message.Message):
+    DESCRIPTOR: google.protobuf.descriptor.Descriptor
+
+    NOW_COL_NAME_FIELD_NUMBER: builtins.int
+    now_col_name: builtins.str
+    def __init__(
+        self,
+        *,
+        now_col_name: builtins.str | None = ...,
+    ) -> None: ...
+    def HasField(self, field_name: typing_extensions.Literal["_now_col_name", b"_now_col_name", "now_col_name", b"now_col_name"]) -> builtins.bool: ...
+    def ClearField(self, field_name: typing_extensions.Literal["_now_col_name", b"_now_col_name", "now_col_name", b"now_col_name"]) -> None: ...
+    def WhichOneof(self, oneof_group: typing_extensions.Literal["_now_col_name", b"_now_col_name"]) -> typing_extensions.Literal["now_col_name"] | None: ...
+
+global___ExprContext = ExprContext
+
 @typing_extensions.final
 class Expr(google.protobuf.message.Message):
     DESCRIPTOR: google.protobuf.descriptor.Descriptor
diff --git a/fennel/testing/query_engine.py b/fennel/testing/query_engine.py
index fa5a2649..824e5e7b 100644
--- a/fennel/testing/query_engine.py
+++ b/fennel/testing/query_engine.py
@@ -8,7 +8,7 @@
 
 import fennel.datasets.datasets
 import fennel.gen.schema_pb2 as schema_proto
-from fennel.expr.expr import NOW_COL_NAME
+from fennel.expr.expr import ExprContext
 from fennel.featuresets import Extractor, Feature, Featureset, is_valid_feature
 from fennel.gen.featureset_pb2 import (
     ExtractorType as ProtoExtractorType,
@@ -23,6 +23,8 @@
     cast_df_to_arrow_dtype,
 )
 
+NOW_COL_NAME = "__ts_col_name__"
+
 
 class QueryEngine:
     """
@@ -376,7 +378,7 @@ def _compute_expr_extractor(
         input_schema[NOW_COL_NAME] = datetime
         df = pd.DataFrame(input_features)
         df[NOW_COL_NAME] = timestamps
-        res = expr.eval(df, input_schema)  # type: ignore
+        res = expr.eval(df, input_schema, context=ExprContext(now_col_name=NOW_COL_NAME))  # type: ignore
         output_dtype = expr.typeof(input_schema)  # type: ignore
         # Cast to correct arrow dtype after evaluating the expression
         res = cast_col_to_arrow_dtype(res, get_datatype(output_dtype))
diff --git a/pyproject.toml b/pyproject.toml
index a7c99a5e..3f8e5acf 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -43,20 +43,20 @@ pyyaml = "^6.0.1"
 
 # For production, we use poetry to build the python package
 
-[build-system]
-requires = ["poetry-core>=1.0.0"]
-build-backend = "poetry.core.masonry.api"
+#[build-system]
+#requires = ["poetry-core>=1.0.0"]
+#build-backend = "poetry.core.masonry.api"
 
 # For local development, we use maturin to build the rust library
 
-# [build-system]
-# requires = ["maturin", "setuptools>=42", "wheel"]
-# build-backend = "maturin"
+[build-system]
+requires = ["maturin", "setuptools>=42", "wheel"]
+build-backend = "maturin"
 
-# [tool.maturin]
-# name = "fennel_data_lib"
-# sdist-directory = "python_package"
-# manifest-path = "../server/fennel_data_lib/Cargo.toml"
+[tool.maturin]
+name = "fennel_data_lib"
+sdist-directory = "python_package"
+manifest-path = "../server/fennel_data_lib/Cargo.toml"
 
 
 # inspired from - https://github.com/pypa/pip/blob/main/pyproject.toml