On this day

A few dates worth marking, and what actually happened on them. Every event and every birthday links to its source, the same rule the comparisons follow.

• What happened on February 29

  The day that only exists every fourth year. Anyone born on it has had roughly a quarter of the birthdays they are owed, which is the kind of arithmetic this whole app exists for.

  15 events · 8 birthdays

• What happened on January 1

  Day one of the count, for everybody at once. Whatever you started measuring this year, this is where the number began.

  17 events · 8 birthdays

• What happened on July 4

  A date most Americans can place instantly, which makes it a useful yardstick: everything below happened on the same square of the calendar.

  17 events · 8 birthdays

• What happened on December 25

  The most fixed point in the western year, and a date people measure other things against without noticing they are doing it.

  17 events · 8 birthdays