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DateFix 2: a real epoch

Version 1 kept every stored value and only changed how the system reads it (7-bit year 0 = 2032). The test on the Tungsten T3 showed where that stops working:

Finding on the T3 Cause
Calendar cannot go back before 2032-01-01, nor forward past 2031-12-31 until the clock itself passes it Datebook compares DateType values as numbers: 2032 (year 0) is "smaller" than 1940
Calendar: DateDay.c, Line:1666, Record not on day when creating an entry in 2032 same – the application's own date logic
Tasks: due date picker shows 1904 for 2032, dates above 2032 impossible applications compute full years as DateType year + 1904
Reset with the clock in 2032 → 2002 the clock value is above maxSeconds; the ROM discards it while booting, before DateFix runs (observed; the T3 ROM itself was not examined)
Alarm on 2032-01-01 fires works: alarms only use seconds

The model

As if the Palm had been shipped with an epoch of 1 January S instead of 1904 (S = start year, 1904…1972 in steps of 4, default 1932; 1940 in 2.0.0-beta.1):

  • The clock counts seconds since S-01-01 (stored value = real time − D days, D = days from 1904-01-01 to S-01-01).
  • A stored DateType year counts from S (2032 with S = 1940 is 92).
  • Applications therefore see a normal, gap-free calendar of internal years 1904…2031 – S…S+127 in reality. Sorting, comparisons, navigation and alarms work without touching any application, and the clock stays below maxSeconds until the end of the window, so a reset keeps it.

Because S − 1904 is a multiple of 4 and the window never reaches 2100, internal and real years have exactly the same leap years: month lengths, day counts and date arithmetic of the internal calendar are correct as they are. Only two things differ from reality, and those are what DateFix patches:

  1. The weekday – internal 1996-01-01 is a Monday, real 2032-01-01 a Thursday: TimSecondsToDateTime (weekDay), DayOfWeek, DayOfMonth.
  2. Year numbers shown to the user – DateToAscii, DateToDOWDMFormat, DateTemplateToAscii get the real year; the date picker (SelectDay) shows and accepts real years.

Data conversion

Existing data was written with S = 1904 and has to be moved by S − 1904 years once (and back when DateFix is disabled or S changes):

  • the clock,
  • DateType/seconds fields of every application whose record format is known – first the documented palmOne PIM databases (Calendar, Tasks, Contacts birthdays), then further time-dependent applications,
  • creation/modification/backup dates of all databases.

Before converting, DateFix copies every affected database to the SD card (/PALM/DateFix/backup/). Dates before S cannot be represented and are reported, not silently changed. Databases with an unknown format are listed as such.

Limitations that remain by design: applications that print years themselves (instead of through the system) show the internal year; data exchanged with a desktop (HotSync conduits) carries internal dates.

Stages (all done unless marked)

  1. Epoch core: patches above, start year setting, clock conversion.
  2. Conversion framework with SD backup; palmOne Calendar, Tasks, Contacts; Expense; database dates.
  3. Date picker with real years (Palm OS 5 through the export tables, Palm OS 3.5 - 4 through the trap table).
  4. Palm OS 3.5 - 4.x: the same model with 68k trap patches.
  5. Open: further applications whose record formats are known (Note Pad, Voice Memo, third-party calendars) and a per-version patch table for applications that draw the year themselves (see ROADMAP.md).