Kilobirthday

A kilobirthday is a celebration of the passage of some multiple of one thousand days since the day of your birth. It may seem arbitrary, but throwing a party when the earth is in approximately the same position relative to the sun as it was on the day for your birthday is arguably pretty arbitrary as well.

As an added bonus, your kilobirthday will cycle through every season once every four kilobirthdays, which is great if you have been saddled by fate with the dreaded summer or holiday birthday.