Worked example

A source date of December 31, 2026 with an owner-chosen lead time of 30 days produces December 1, 2026.

How the calculation works

The tool subtracts calendar days at UTC midnight, so daylight-saving clock changes do not add or remove a day. Zero lead time gives the source date. Leap days are included when the calendar contains them.

What the result does not establish

This does not calculate a legal deadline or schedule a notification. Verify the source date. Enter any desired reminder separately in the app.

Keep the connected record.

Coldbore keeps firearm identity, photos, documents, maintenance, and range sessions together on your iPhone or iPad.

Unlimited records, ordinary reports, exports, iCloud Backup, and app lock stay free. Collection Check, Collection Pack, Renewals, and Costs and history need optional membership.

Get Coldbore free

iOS 17 or iPadOS 17 and later. No Coldbore account.

Reviewed October 2, 2026.