Daily Plan - use of different time zones

Current Situation

• If time zones are configured with Settings->dailyplan->time_zone, and the time zone of a schedule doesn't match, then the Daily Plan entries can either be assigned to the next day or will not be added at all.
• Daily Plan Calculation Details:
  • The calculation to determine if a given start time aligns with a Daily Plan date involves two checks:
    • FrequencyResolver
      • This component identifies working days based on the calendar and schedule definitions
        • Calculates the days for the given Daily Plan date and for the following day
        • It may return two days if the next day is considered a working day
    • PeriodResolver
      • This uses Settings->dailyplan->time_zone to determinate the begin and end of a given day's period
      • This check examines whether the start time of a day calculated by the FrequencyResolver matches the specified Daily Plan date

Current Situation Examples

• Settings->dailyplan->time_zone= Etc/UTC, period_begin=00:00
• Daily Plan date: 2023-10-25

1. Schedule with a single start at 01:00(Europe/Berlin)
   • calculated Daily Plan day period for 2023-10-25 based on Daily Plan Settings:
     • (UTC)2023-10-25 00:00:00 to 2023-10-26 00:00:00
   • calculated start based on the DailyPlan, Schedule settings and FrequencyResolver day:
     • FrequencyResolver day=2023-10-25
     • (UTC)2023-10-24 23:00:00
       • skipped because it's not within the DailyPlan day period
     • FrequencyResolver day=2023-10-26 (this iteration for 2023-10-26 only occurs if the FrequencyResolver has delivered 2 days (2023-10-25, 2023-10-26))
       • (UTC)2023-10-25 23:00:00
         • added, but for the next day
2. Schedule with a single start at 22:30(America/Chicago)
   • calculated the DailyPlan Day period for 2023-10-25 based on DailyPlan Settings
     • (UTC)2023-10-25 00:00:00 to 2023-10-26 00:00:00
   • calculated Start based on the DailyPlan, Schedule settings and FrequencyResolver day
     • FrequencyResolver day=2023-10-25
     • (UTC)2023-10-26 03:30:00
       • skipped because it's not within the DailyPlan Day period
     • FrequencyResolver day=2023-10-26 (this iteration for 2023-10-26 only occurs if the FrequencyResolver has delivered 2 days (2023-10-25, 2023-10-26))
     • (UTC)2023-10-27 03:30:00
       • skipped because it's not within the DailyPlan Day period
   • as aresult this start time will never be added to the DailyPlan

Desired Behavior
Daily Plan dates should be accurately calculated for Daily Plan settings

Maintainer Note

• The time zone defined within the Settings->dailyplan should impact the start of the Daily Plan service only.
• The frequency calculation is based on a single day, which is the DailyPlan date.
• The period calculation relies on the time zone specified by the schedule.

Test Instructions

• use different time zones for Settings->dailyplan and schedule.
• use different start times (e.g. at begin and end of a day)
• use periods with single start(s) and repeated periods
• use default(00:00:00) Settings->dailyplan->period_begin and different from midnight(see JOC-1329)
• use non-working days feature tests (see JOC-1484)
• create DailyPlan manually and via the DailyPlan Service