Bug #17042: Times with timezones return incorrect week numbers

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.8.0dev (2020-07-15 master 79d06483a8)
• Backport: 2.5: DONTNEED, 2.6: REQUIRED, 2.7: REQUIRED

[timcraft (Tim Craft)]

Times with timezones return incorrect week numbers from strftime. For example:

$ irb -r tzinfo
irb(main):001:0> Time.utc(2020, 7, 22, 12, 0, 0).strftime('%U %V %W')
=> "29 30 29"
irb(main):002:0> Time.new(2020, 7, 22, 12, 0, 0, TZInfo::Timezone.get('America/New_York')).strftime('%U %V %W')
=> "00 00 00"

Follow up to #17024

[S_H_ (Shun Hiraoka)]

Same behaviour in 2.7 & 2.6(checked 2.7.1, 2.7.0, 2.6.6, 2.6.5).

[S_H_ (Shun Hiraoka)]

Apparently the calculation result ret = ((timeptr->tm_yday + 7 - wday) / 7); is negative(timeptr->tm_yday is negative).

static int
weeknumber(const struct tm *timeptr, int firstweekday)
{
	int wday = timeptr->tm_wday;
	int ret;

	if (firstweekday == 1) {
		if (wday == 0)	/* sunday */
			wday = 6;
		else
			wday--;
	}
	ret = ((timeptr->tm_yday + 7 - wday) / 7);
	if (ret < 0)
		ret = 0;
	return ret;
}

[S_H_ (Shun Hiraoka)]

This code resolve this behaviour.

static VALUE
time_strftime(VALUE time, VALUE format)
{
    struct time_object *tobj;
    const char *fmt;
    long len;
    rb_encoding *enc;
    VALUE tmp;

    GetTimeval(time, tobj); 
    if (tobj->vtm.yday == 0) {
        VALUE zone = tobj->vtm.zone;
        if (!NIL_P(zone)) zone_localtime(zone, time);
    }
    MAKE_TM(time, tobj);
    StringValue(format);
    if (!rb_enc_str_asciicompat_p(format)) {
	rb_raise(rb_eArgError, "format should have ASCII compatible encoding");
    }
    tmp = rb_str_tmp_frozen_acquire(format);
    fmt = RSTRING_PTR(tmp);
    len = RSTRING_LEN(tmp);
    enc = rb_enc_get(format);
    if (len == 0) {
	rb_warning("strftime called with empty format string");
	return rb_enc_str_new(0, 0, enc);
    }
    else {
        VALUE str = rb_strftime_alloc(fmt, len, enc, time, &tobj->vtm, tobj->timew,
				      TZMODE_UTC_P(tobj));
	rb_str_tmp_frozen_release(format, tmp);
	if (!str) rb_raise(rb_eArgError, "invalid format: %"PRIsVALUE, format);
	return str;
    }
}

tobj->vtm.ydayis seems to be 0.

So, these code resolve.

    if (tobj->vtm.yday == 0) {
        VALUE zone = tobj->vtm.zone;
        if (!NIL_P(zone)) zone_localtime(zone, time);
    }

[S_H_ (Shun Hiraoka)]

Created patch.

https://github.com/ruby/ruby/pull/3352

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset git|8ed687a4d7b7a77f30f8e937f58aae74bfb699b6.

---

Test for weeknumber with timezone [Bug #17042]

[nobu (Nobuyoshi Nakada)]

• Backport changed from 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN to 2.5: DONTNEED, 2.6: REQUIRED, 2.7: REQUIRED