Free tool

Billing cycle date calculator

List upcoming invoice dates for daily, weekly, monthly and yearly cycles.

  1. #1Fri, 31 Jan, 2025
  2. #2Fri, 28 Feb, 2025month end
  3. #3Mon, 31 Mar, 2025
  4. #4Wed, 30 Apr, 2025month end
  5. #5Sat, 31 May, 2025
  6. #6Mon, 30 Jun, 2025month end

What it calculates

Monthly billing looks simple until a subscription starts on the 31st. Short months have no 31st, so a well-behaved system clamps to the last day of that month but keeps the original day as the anchor, so March goes back to the 31st.

The formula

  • Daily: start + n days; weekly: start + 7n days
  • Monthly: same day of the month, clamped to the last day of shorter months
  • Yearly: same day and month, 29 February falls back to 28 February in non-leap years
  • Each date is computed from the original start, never from the previous clamped date

Worked example

Monthly subscription starting 31 January 2025

  1. Invoice 1: 31 Jan 2025
  2. Invoice 2: 28 Feb 2025 (February has 28 days)
  3. Invoice 3: 31 Mar 2025 (back to the anchor day)
  4. Invoice 4: 30 Apr 2025 (April has 30 days)

Questions

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