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Adjust comments in time.asm to reflect actual starting date of time_t.

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It was clearly supposed to be 1 Jan 1970, but it's actually not, probably because the number of days from 1 Jan 1900 to 1 Jan 1970 was miscalculated. Changing it now could potentially cause compatibility issues (especially for GNO, which uses time_t in some kernel call interfaces and file formats), so for now it is left as is and just documented appropriately.

Nothing in the C standards requires the time_t epoch to be 1 Jan 1970, so this does not cause any standards-compliance problem for the C standards. (It is different from POSIX, though.)
This commit is contained in:
Stephen Heumann 2022-12-29 14:25:24 -06:00
parent e2de990f4d
commit d30ee1a2e5
1 changed files with 13 additions and 12 deletions
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25
time.asm
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@ -30,7 +30,7 @@ Time start dummy segment
*
TimeCommon privdata
;
; For conversion to/from seconds since 1970
; For conversion to/from seconds since 13 Nov 1969
;
year ds 4 year 0..99
month ds 4 month 1..12
@ -38,7 +38,7 @@ day ds 4 day 1..31
hour ds 4 hour 0..23
minute ds 4 minute 0..59
second ds 4 second 0..59
count ds 4 seconds since 1 Jan 1970
count ds 4 seconds since 13 Nov 1969
t1 ds 4 work variable
t2 ds 4 work variable
@ -225,20 +225,20 @@ mk1 inx
****************************************************************
*
* factor - compute the seconds since 1 Jan 1970 from date
* factor - compute the seconds since 13 Nov 1969 from date
*
* Inputs:
* year,month,day,hour,minute,second - time to convert
*
* Outputs:
* count - seconds since 1 Jan 1970
* count - seconds since 13 Nov 1969
*
****************************************************************
*
factor private
using TimeCommon
;
; compute the # of days since 1 Jan 1970
; compute the # of days since 13 Nov 1969
;
mul4 year,#365,count count := 365*year + day + 31*(month-1)
add4 count,day
@ -269,8 +269,9 @@ lb3 add4 t2,#300 count := count -
mul4 t2,#3
div4 t2,#4
sub4 count,t2
sub4 count,#25516 subtract off days between 1 Jan 00 and
! 1 Jan 70
sub4 count,#25516 subtract off days between 1 Jan 1900
! and 13 Nov 1969, minus 2 to adjust for
! skipped leap days in 1700 and 1800
;
; Convert to seconds and add in time of day in seconds
;
@ -289,7 +290,7 @@ lb3 add4 t2,#300 count := count -
* time_t *t;
*
* Inputs:
* t - pointer to # of seconds since 1 Jan 1970
* t - pointer to # of seconds since 13 Nov 1969
*
* Outputs:
* returns a pointer to a time record for UTC time
@ -375,7 +376,7 @@ lb2 jsl ~gmlocaltime use common gmtime/localtime code
* time_t *t;
*
* Inputs:
* t - pointer to # of seconds since 1 Jan 1970
* t - pointer to # of seconds since 13 Nov 1969
*
* Outputs:
* returns a pointer to a time record for local time
@ -422,7 +423,7 @@ lb1 plb
* ~gmlocaltime - common code for gmtime and localtime
*
* Inputs:
* t - time_t value (# of seconds since 1 Jan 1970)
* t - time_t value (# of seconds since 13 Nov 1969)
* isdst - value for tm_isdst flag
*
* Outputs:
@ -522,7 +523,7 @@ tm_isdst ds 2 daylight savings? 1 = yes, 0 = no
* Outputs:
* tmptr->wday - day of week
* tmptr->yday - day of year
* returns the ime in seconds since 1 Jan 1970
* returns the ime in seconds since 13 Nov 1969
*
****************************************************************
*
@ -561,7 +562,7 @@ temp2 equ 5 temp variable
sta minute
lda [tmptr]
sta second
jsr factor compute seconds since 1970
jsr factor compute seconds since 13 Nov 1969
move4 count,temp save the value for later return
lda #1 compute the days since the start of the
sta month year