Twins

• Most twins share the same birthday (Day, Month, Year).
• An exception occurs when one twin is born before midnight and the other is born after.
• Another exception occurs when one twin is born on New Year’s Eve and the other is born on New Year.

Same Month

• If there are more than 13 people, then at least two must share the Month in their birthdays.
• It follows the Pigeon Hole Principle.

Same Month and Day

• If there are more than 30 people, then there is a high likelihood that at least two share the Day and the Month in their birthdays.
• It follows from Probability and Statistics.

Distribution

• In a group, the birthdays are not equally distributed.
• For instance, my two sisters and I are all born in August.
  There are seven siblings.

Freebie

• Some restaurants do not charge the Birthday Person (Boy, Girl) if there are three more persons in the group.
• They will ask and verify the ID.

Happy Birthday

• “Happy Birthday” song is one of the most played songs.
• In the early days, the song received a lot of royalties.
• Now, it is considered to be in the free public domain.

February 29 born

• Do they celebrate only in Leap Years?
• Do they celebrate on February 28 or March 1st?

Different Calendars

Some celebrate their birthday twice : once using the Gregorian Calendar and once using the Myanmar luni-solar Calendar.