What does a 0-day grace duration mean?

Expiration begins immediately, following whichever convention is selected, and the receipt notes that directly rather than leaving it implied.

Which convention is more common in practice?

Both appear regularly, which is exactly why this always states the selected convention explicitly rather than assuming one, since a governing document could reasonably use either.

Grace Period / Expiration Calculator

Enter a start date, a grace duration, and which convention counts the start date. This is a planning calculation from the rule you enter, not a legal determination of a grace period or expiration date.

Need this rule applied to a repeating trigger instead? See Rolling Deadline Calculator.

Want to learn more?

SLA Deadlines and Grace Periods Are Not the Same Clock

Worked example

A 5-day grace period starting January 4, 2027, under the "start counts as day 1" convention puts the last day of grace on January 8 and expiration beginning January 9. Switch that same 5-day period to the "grace begins the day after start" convention instead, and the last day shifts one day later, to January 9, with expiration now beginning January 10, the two conventions genuinely disagreeing by exactly one day for the identical stated duration.

Common mistakes

Assuming "5 days" always means the same boundary date regardless of which convention a policy actually uses. The two conventions can differ by exactly one day for the same stated duration.
Skipping the convention field because it seems minor. That single choice is exactly what determines the correct boundary date.

Limitations

This does not determine a legally binding grace period or expiration date. Check the actual governing document for the convention it genuinely uses before treating this result as final.

Frequently asked questions

What does a 0-day grace duration mean?: Expiration begins immediately, following whichever convention is selected, and the receipt notes that directly rather than leaving it implied.
Which convention is more common in practice?: Both appear regularly, which is exactly why this always states the selected convention explicitly rather than assuming one, since a governing document could reasonably use either.