Why Does Pytz's `Asia/Hong_Kong` Timezone Show Inconsistent Offsets?

Datetime Anomalies with Pytz Timezones

Pytz, a prevalent Python library for handling timezones, sometimes presents unusual offset behavior. Notably, when requesting the 'Asia/Hong_Kong' timezone, pytz may return an offset of 7:37:00, which appears inconsistent.

To illustrate, consider the following code:

import pytz
pytz.timezone('Asia/Hong_Kong')

The output shows the timezone information as:

<DstTzInfo 'Asia/Hong_Kong' LMT+7:37:00 STD>

Inconsistently, utilizing the localize method to attach the Hong Kong timezone to a datetime instance yields different results:

hk = pytz.timezone('Asia/Hong_Kong')
hk_dt = hk.localize(datetime(2012, 1, 1))

Comparing the datetimes reveals:

dt1 = datetime(2012,1,1,tzinfo=hk)
if dt1 > hk_dt:
    print "Why?"

Unexpectedly, dt1 is evaluated as greater than hk_dt.

Explanation

This anomaly arises due to changes in time zones and offsets over time. Pytz assigns the oldest available name and offset to each timezone object it creates. However, when utilizing the localize method to attach the zone to a date, it incorporates the accurate name and offset corresponding to the specified time.

In conclusion, simply employing the datetime constructor to assign a timezone to a date precludes it from adjusting correctly, leading to the observed inconsistency.

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