What the day logo
What the Day
LearnPracticePlayDailyGuides
LearnGuidesPracticePlayDaily challengeLeaderboardAboutContactPrivacy
Copyright © 2026 Jesper Kiledal
All rights reserved
☕Buy me a coffee
What the day logo
What the Day
LearnPracticePlayDailyGuides

June 21, 1999 was a
Monday

June 21, 1999 was a Monday — that’s 9,850 days ago. Below you can see exactly how to work the weekday out in your head with the Doomsday algorithm, along with a few other facts about the date.

Weekday
Monday
Day of year
172 of 365
ISO week
Week 25
Leap year?
No
Zodiac sign
Cancer
Days ago
9,850

How to solve: June 21, 1999

  1. 1
    Century anchor1900s→Wednesday (3)
    Practice →
  2. 2
    Divide by 1299 ÷ 12→8
    Practice →
  3. 3
    Remainder of 1299 % 12→3
    Practice →
  4. 4
    Divide remainder by 43 ÷ 4→0
    Practice →
  5. 5
    Year's doomsday(3 + 8 + 3 + 0) % 7→0 → Sunday
    Practice →
  6. 6
    Month doomsdayJune→6th
    Practice →
  7. 7
    Distance21 − 6→15
    Practice →
  8. 8
    Final answer(0 + 15) % 7→1 → Monday

On this day in history

  • 1982Birth of Prince William

Related dates

Day beforeJune 20, 1999 — SundayDay afterJune 22, 1999 — TuesdayOne year earlierJune 21, 1998 — SundayOne year laterJune 21, 2000 — Wednesday
Want to be able to do this for any date in seconds? Read the guide or practice the algorithm.
Did you know? Did you know that the third Monday of January is often referred to as 'Blue Monday' and is considered the most depressing day of the year?