tmparse: put in local timezone hack

Ctime is defined as printing a 3-character timezone
name. The timezone name is ambiguous. For example,
EST refers to both Australian and American eastern
time. On top of that, we don't want to make the
tzabbrev table exhaustive. So, we put in this hack:

Before we consult the well known table of timezones,
we check if the local time matches the timezone name.

On top of that, tm2sec

If you want unambiguous timezone parsing, use numeric
timezone offsets (Z, ZZ formats).

1 files changed, 27 insertions, 1 deletions

diff --git a/sys/src/libc/port/date.c b/sys/src/libc/port/date.c
index 189bcb438..44ae15696 100644
--- a/sys/src/libc/port/date.c
+++ b/sys/src/libc/port/date.c
@@ -615,7 +615,7 @@ tmparse(Tm *tm, char *fmt, char *str, Tzone *tz, char **ep)
 	int depth, n, w, c0, zs, z0, z1, md, ampm, zoned, sloppy, tzo, ok;
 	vlong abs;
 	char *s, *p, *q;
-	Tzone *zparsed;
+	Tzone *zparsed, *local;
 	Tzabbrev *a;
 	Tzoffpair *m;
 
@@ -774,6 +774,32 @@ tmparse(Tm *tm, char *fmt, char *str, Tzone *tz, char **ep)
 			switch(w){
 			case -1:
 			case 3:
+				/*
+				 * Ugly Hack:
+				 * Ctime is defined as printing a 3-character timezone
+				 * name. The timezone name is ambiguous. For example,
+				 * EST refers to both Australian and American eastern
+				 * time. On top of that, we don't want to make the
+				 * tzabbrev table exhaustive. So, we put in this hack:
+				 *
+				 * Before we consult the well known table of timezones,
+				 * we check if the local time matches the timezone name.
+				 *
+				 * If you want unambiguous timezone parsing, use numeric
+				 * timezone offsets (Z, ZZ formats).
+				 */
+				if((local = tzload("local")) != nil){
+					if(cistrncmp(s, local->stname, strlen(local->stname)) == 0){
+						s += strlen(local->stname);
+						zparsed = local;
+						goto Zoneparsed;
+					}
+					if(cistrncmp(s, local->dlname, strlen(local->dlname)) == 0){
+						s += strlen(local->dlname);
+						zparsed = local;
+						goto Zoneparsed;
+					}
+				}
 				for(a = tzabbrev; a->abbr; a++){
 					n = strlen(a->abbr);
 					if(cistrncmp(s, a->abbr, n) == 0 && !isalpha(s[n]))