fixup! refactor(date): improve type hints

lua/orgmode/objects/date.lua

@@ -11,10 +11,11 @@ local time_format = '%H:%M'
 
 ---@alias OrgDateSpan 'minute' | 'hour' | 'day' | 'week' | 'month' | 'year'
 
----@class OsTime
+---@alias OsTime number
 
 ---@class OsDate
 ---@field day number?
+---@field wday string?
 ---@field month number?
 ---@field year number?
 ---@field hour number?
@@ -59,9 +60,6 @@ local Date = {
   end,
 }
 
----@alias DateTbl { year: number, month: number, day: number, hour: number, min: number }
----@alias DateTblWithSec { year: number, month: number, day: number, hour: number, min: number, sec: number }
-
 ---@param source table
 ---@param target? table
 ---@param include_sec? boolean
@@ -535,7 +533,7 @@ end
 function Date:get_weekday()
   ---@type table
   ---@diagnostic disable-next-line: assign-type-mismatch
-  local date = os.date('*t', self.timestamp)
+  local date = os_date(self.timestamp)
   return date.wday
 end