6 Month Calculator - Add or Subtract Months from Any Date
Enter a starting date and pick how many months to add or subtract. The calculator shows the result date, the day of the week it falls on, and a timeline placing both dates in context. Switch to "months between two dates" mode to count how many complete months separate any two calendar dates.
What the 6 month calculator does
This tool adds or subtracts any number of months to or from a calendar date. The most common use is adding exactly 6 months (one half-year), which is relevant for lease renewals, loan deferrals, probation review dates, passport expiry checks, and subscription anniversaries. You can change the month count to any whole number between 0 and 1200, so it works equally well for 3-month quarters, 9-month project timelines, or any other planning horizon. A third mode counts the complete months between two dates and shows the leftover days.
How months are added and subtracted
Adding months rolls the calendar forward by whole months while keeping the same day of the month. January 15 plus 6 months is July 15. The only complication is month-end overflow: if the starting day does not exist in the target month, the calculator clamps to the last valid day. For example, January 31 plus 1 month becomes February 28 (or February 29 in a leap year), because February has no 31st. The same logic applies in reverse when subtracting months. This matches the behavior used by most financial contracts, HR systems, and scheduling software.
Counting months between two dates
The "months between" mode counts how many complete months fit between a start and an end date, then reports the leftover days separately. A complete month passes only once the same calendar day in the next month is reached. For instance, the span from March 10 to August 5 contains 4 complete months (March 10 to July 10) plus 26 extra days, not 5 months, because August 10 has not yet arrived. This matches how landlords, banks, and courts count lease and loan durations.
Practical uses for 6 month calculations
Six months appears frequently in legal and financial deadlines. Many lease agreements run on 6-month or 12-month terms; adding 6 months to the start date gives the renewal or notice-to-quit window. Employment probation periods are often 3 or 6 months. Tax authorities in several countries set 6-month extensions on filing deadlines. Warranties and insurance policies commonly run for 6, 12, or 24 months. Passport agencies recommend renewing at least 6 months before the expiry date because many countries require 6 months of remaining validity for entry. Knowing the exact calendar date removes ambiguity and avoids costly miscalculations.
Common month milestones
| Months | Common name | Calendar days (approx.) |
|---|---|---|
| 1 | 1 month | 28-31 |
| 3 | 1 quarter | 89-92 |
| 6 | Half year | 181-184 |
| 9 | 3 quarters | 273-276 |
| 12 | 1 year | 365-366 |
| 18 | 18 months | 546-549 |
| 24 | 2 years | 730-731 |
Reference dates for typical planning periods.
Frequently asked questions
What date is 6 months from today?
Set the start date to today (the default) and the number of months to 6, then read the result date. For example, if today is January 15, 6 months later is July 15. If today is August 31, 6 months later is February 28 (or 29 in a leap year) because February has fewer days.
What date is 6 months before today?
Switch the mode to "Subtract months," set the start date to today, and leave the month count at 6. The calculator counts 6 months backward and returns the earlier date.
How are months counted when the start day does not exist in the result month?
The calculator clamps to the last valid day of the target month. Adding 1 month to January 31 gives February 28 (or February 29 in a leap year); adding 1 month to March 31 gives April 30. This is called "end-of-month clamping" and matches how most financial and legal systems handle month arithmetic.
Is 6 months always the same as 180 days?
No. Six calendar months can span 181 to 184 days depending on which months are involved and whether a leap year falls in the range. For example, January through June covers 181 days in a common year and 182 in a leap year. If you need an exact day count rather than a calendar-month count, use a days calculator instead.
How do I count the months between two dates?
Select "Months between two dates" mode, enter your start and end dates, and the calculator returns the number of complete months plus the leftover days. A complete month is counted only when the same day-of-month is reached in the later month.
Can I calculate more than 6 months?
Yes. Change the number of months field to any value from 0 to 1200. The calculator works for any month span, whether you need 3 months, 18 months, or 10 years.