OS.get_datetime_from_unix_time() does not return the same value as OS.get_datetime()

[ghost]

Godot version

3.4-beta4

System information

Windows 10

Issue description

The docs for OS.get_datetime_from_unix_time() say:

The returned Dictionary's values will be the same as get_datetime, with the exception of Daylight Savings Time as it cannot be determined from the epoch.

But that's not true. Unless the 7 hours difference is because of Daylight Savings? I don't really know if this is a bug or not or intended behavior.

Steps to reproduce

1. Make a new project.
2. Use this code:

     func _ready() -> void:
         print(OS.get_datetime())
         print(OS.get_datetime_from_unix_time(OS.get_unix_time()))

Minimal reproduction project

No response

[akien-mga]

What results fo you get? And what's your timezone?

[gelvinp]

Windows stores its RTC time in local time (i.e. in your time zone) while Mac and most linux systems store time in UTC. If OS.get_unix_time() is reading from this RTC then it would be 7 hours off if you were in mountain standard time, for example.

It's possible to configure windows to store UTC instead through a registry modification, but you should be careful if you want to see if that "fixes" the bug. When I get home today I can try myself and I'll report back.

I take it back, on my Mac OS machine the output of the above is:

{day:22, dst:False, hour:16, minute:3, month:9, second:49, weekday:3, year:2021}
{day:22, hour:23, minute:3, month:9, second:49, weekday:3, year:2021}

These are definitely 7 hours off. For reference my timezone is MST (-7)

[ghost]

My output is

{day:22, dst:False, hour:16, minute:9, month:9, second:41, weekday:3, year:2021}
{day:22, hour:23, minute:9, month:9, second:41, weekday:3, year:2021}

My timezone is PDT (-7) also.

[akien-mga]

Here's what I have on Linux in CEST / UTC+2 with DST on (Summer Time), with current time 10:10 CEST / 08:10 UTC:

{day:23, dst:True, hour:10, minute:10, month:9, second:6, weekday:4, year:2021}
{day:23, hour:8, minute:10, month:9, second:6, weekday:4, year:2021}

So the output seems consistent to me, it's just the documentation which is wrong:

• OS.get_datetime() is local time. If local timezone has DST, dst should be true.
• OS.get_datetime_from_unix_time() gives UTC time.

One apparent issue though is that @ShatReal should have dst:True if in PDT timezone - unless the OS is not actually configured to track PST / PDT but the current local time was just hardcoded manually.

[mhilbrunner]

Note: Time stuff was moved out of OS to Time in the mean time (:P): #49123