Illustrative example. The dates and amounts below are provided for practice.
A first meeting was February 1, 2027, a first date was February 14, and the couple agreed they were together on March 10. They want to compare those memories as of April 1.
Calculate all three memories
Run February 1 through April 1 to measure time since meeting. The elapsed interval is 59 days, giving inclusive Day 60. Run February 14 through April 1 for the first-date count. The elapsed interval is 46 days, giving inclusive Day 47.
Then run March 10 through April 1. The elapsed interval is 22 days, giving inclusive Day 23. Keep the end date fixed so the difference reflects only the chosen start.
Decide what the celebration describes
A caption saying “Day 47 since our first date” uses the February 14 start. A relationship day count should use the date the couple agrees marks that relationship.
The first date and relationship start are 24 days apart; the meeting and relationship start are 37 days apart. Those gaps explain the different counts without making one memory more important.
Save separate records with recognizable titles if both deserve a place in the calendar. Avoid editing the start back and forth on a single saved event, because that makes an old countdown screenshot difficult to interpret. The calculator itself can be used without saving either date.