From e2de990f4d5c608cc191ad9d94a2df27571d22a5 Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Wed, 28 Dec 2022 19:55:48 -0600
Subject: [PATCH] strftime: use Time Tool Set to get time zone offset.

This is used for the %z conversion specifier (giving the time zone offset in +-HHMM format). The %Z conversion specifier (giving the locale's time zone name or abbreviation) also prints the same thing for now.

As with gmtime, this will only use the Time Tool Set if it has already been started. Otherwise, these conversions simply produce no output.
---
 time.asm    | 54 ++++++++++++++++++++++++++++++++++++++++++++++++-----
 time.macros |  5 +++++
 2 files changed, 54 insertions(+), 5 deletions(-)

diff --git a/time.asm b/time.asm
index f323c77..9cbc246 100644
--- a/time.asm
+++ b/time.asm
@@ -1098,12 +1098,56 @@ Y_skip   inx
          rts
 
 ;%z - offset from UTC, if available
-;we print nothing, because time zone info is not available
-fmt_z    rts
-
 ;%Z - time zone name or abbreviation, if available
-;we print nothing, because time zone info is not available
-fmt_Z    rts
+;we print the numeric offset for both, or nothing if time zone is not available
+fmt_z    anop
+fmt_Z    pha                            check if time tool is active
+         _tiStatus
+         pla
+         bcs   z_ret
+         beq   z_ret
+         pea   0                        push pointer to string buffer
+         tdc
+;        clc
+         adc   #numstr
+         pha
+         pha                            make space for TZ preferences record
+         pha
+         pea   1                        get one record element only (TZ offset)
+         tsc                            get time zone preference
+         inc   a
+         pea   0
+         pha
+         _tiGetTimePrefs
+         pla
+         bcc   z_dst
+z_bail   pla                            bail out in case of error
+         pla
+         pla
+         pla
+z_ret    rts
+z_dst    ldy   #tm_isdst                adjust for DST (+1 hour) if needed
+         lda   [timeptr],y
+         bmi   z_bail                   bail out if DST is unknown
+         beq   z_fmtstr
+;        clc
+         pla
+         adc   #60*60
+         tay
+         pla
+         adc   #0
+         pha
+         phy
+z_fmtstr pea   0                        no DST mangling
+         _tiOffset2TimeZoneString       get TZ offset string
+         bcs   z_ret
+         ldx   #1
+z_loop   lda   numstr,x                 print the digits
+         jsr   writech
+         inx
+         cpx   #5+1
+         blt   z_loop
+         rts
 
 fmt_invalid rts
 
diff --git a/time.macros b/time.macros
index c9db57c..e291e83 100644
--- a/time.macros
+++ b/time.macros
@@ -631,3 +631,8 @@
 &lab ldx #$0938
  jsl $E10000
  MEND
+ MACRO
+&lab _tiOffset2TimeZoneString
+&lab ldx #$1138
+ jsl $E10000
+ MEND