So does that mean her birthday changes from year-to-year? (According to my calendar, the first day of autumn this year is September 23.) Oh, well... I guess it's than her cousin, who celebrates a birthday only once every four years!
Because this year's autumnal equinox falls so early in the morning in UTC, it is on the previous night in locations a few time zones west of Greenwich. In the United States, the autumnal equinox will be at 11:09 PM EDT, 10:09 PM CDT, 9:09 PM MDT, and 8:09 PM PDT on September 22.
The autumnal equinox, or the first day of fall in the northern hemisphere, will be September 22, in the United States and locations further west. The September 2010 equinox will however be on September 23 in Greenwich, England, Europe, and more easterly locations.
So does that mean her birthday changes from year-to-year?
If Krypton's year was of a different length to Earth's, her Kryptonian birthday(1) would coincide with a different Earth day every year. (And probably not exactly with a particular day in Supergirl's time zone. If a Kryptonian day were longer than an Earth day, it might overlap with three or more days in her time zone.)
(1) The pre-Crisis Supergirl was born after the destruction of Krypton in Argo City, but presumably its inhabitants employed an artificial day based on the length of the Kryptonian day and followed the Kryptonian calendar.
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The autumnal equinox, or the first day of fall in the northern hemisphere, will be September 22, in the United States and locations further west. The September 2010 equinox will however be on September 23 in Greenwich, England, Europe, and more easterly locations.
If Krypton's year was of a different length to Earth's, her Kryptonian birthday(1) would coincide with a different Earth day every year. (And probably not exactly with a particular day in Supergirl's time zone. If a Kryptonian day were longer than an Earth day, it might overlap with three or more days in her time zone.)
(1) The pre-Crisis Supergirl was born after the destruction of Krypton in Argo City, but presumably its inhabitants employed an artificial day based on the length of the Kryptonian day and followed the Kryptonian calendar.