Calculate a starting date from an end date and a period.
Use this when you know the final deadline but need to estimate the starting date or counting date.
You can combine years, months, weeks, and days in one entry. Example: 1 year 6 months 2 weeks.
Enter the dates and period
to see the result
All results are reference information based on general principles of the Korean Civil Act. Actual legal effect and deadline outcomes can vary depending on the facts, special agreements, and other applicable statutes. Consult a qualified professional before relying on the result for an important legal action.
It applies Korean Civil Act period-counting logic in reverse. The calculator works backward from the end date and keeps the day-one rule consistent with the option you selected.
If the deadline you entered is already the extended date, turn on the input end-date option. The calculator will first restore the original last day and then count backward from there.
Only as a reference. Procedural deadlines and limitation periods can follow special rules outside the general Korean Civil Act baseline, so important matters should be reviewed separately with a professional.
This page is reviewed against the official sources below. Special statutes, case-specific agreements, or procedural rules can still change the final legal outcome.
Official statutory source used to review the general baseline for day-one counting, period expiry, calendar-based month and year counting, and holiday extension.
Official public-holiday data source referenced when the calculator checks Korean public holidays and substitute holidays.