DST fix: adjusting time in appointments

Calcurse saves time and date information on disk as local time in readable text
file format. When loaded from disk or when entered by the user, local time is
converted to Unix time (seconds since 00:00:00, 1 January 1970). When
displayed, and later when saved to disk, the Unix time is converted back to
readable local time. Both conversions depend on DST.

Hence, if midnight for a day with DST in effect (i.e. local time) is converted,
increased with an amount and converted back, the amount has changed if DST is
_not_ in effect for the resulting time. In general, calculations on Unix time
variables should be used with caution because of the DST-dependent conversions.
Instead, the calculations should be performed on local time data with the help
of mktime().

The commit fixes start time for pasted appointments (ordinary and recurrent)
and the 'until'-date of recurrent appointments, pasted as well as new and
edited. The latter problem is slightly different in that the adjustment is a
number of days, as it is for exception dates.

Update of the date in parse_datetime() has been corrected to be similar to
update of the time, although no problem has been identified.

Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/ui-day.c b/src/ui-day.c
index 9a118dc..979ecc0 100644
--- a/src/ui-day.c
+++ b/src/ui-day.c
@@ -332,7 +332,7 @@ static void update_rept(struct rpt **rpt, const long start)
 				keys_wgetch(win[KEY].p);
 				continue;
 			}
-			newuntil = start + days * DAYINSEC;
+			newuntil = date_sec_change(start, 0, days);
 		} else {
 			int year, month, day;
 			if (!parse_date(timstr, conf.input_datefmt, &year,
@@ -836,7 +836,7 @@ void ui_day_item_repeat(void)
 				keys_wgetch(win[KEY].p);
 				continue;
 			}
-			until = p->start + days * DAYINSEC;
+			until = date_sec_change(p->start, 0, days);
 		} else {
 			int year, month, day;
 			if (!parse_date(user_input, conf.input_datefmt,