There are 366 possible birthdays (including February 29 in a leap year) and this blog has many more than 367 readers.

包括润年的2月29日在内，全年366天中的某一天都可以成为某人的生日。

youdao

In a Leap year, we have 29 days in February, while in a usual year we have only 28 days.

在闰年，我们在二月29天，而在平常的一年，我们只有28天。

youdao

Companies' monthly financial reports may run fine for years, then crash in February of a leap year when software tries to compare Feb. 29, 2012, to a nonexistent Feb. 29, 2011.

WSJ: For Some, All in a Leap Day's Work