Month Calculator & Counter

1. How to use this month calculator / counter
2. How to calculate the number of months between dates
3. What calendar is used in the month calculator

    How to use this month calculator / counter

Finding out how many months there are between two dates is a common task in time planning and scheduling. For example, it can be used to estimate the number of months available to finish an assignment given some deadline, or to calculate the duration of a long trip or business travel assignment. A month counter can also be useful in analyses that require the calculation of the duration of past events with a known start and end date.

To use the tool, simply enter the start and the end date of the time period. For example, if a work assignment has a deadline on Dec 21, 2023, simply enter the current date in the first field and Dec 21, 2023 and press the button to get an exact count of the number of full months in between, as well as exact duration in months and days.

Similarly, if you are interested in the number of months since a given date in the past, just enter it in the "Start Date" field and select the present date in the second. The months calculator will return the number of full calendar months since, as well as the exact number of months and days since, while accounting for leap years.

    How to calculate the number of months between dates

When calculating the number of months between dates separated by a longer period of time, leap year adjustments need to be considered or one can be off by a month or more in certain scenarios. What also makes it difficult is that different months have a different number of days. Some months have 30 days, others 31 days, and February has only 28 days in a typical year and 29 days in a leap year. Using a month counter means you need not worry about these complications.

If calculating the number of months between two dates by hand, the following table can be useful for adjusting the count based on the number of days in any given month:

Neither difference in number of days in each month, nor leap years play a role when calculating the number of full months between two exact dates. For example, the time period between Mar 1 and Oct 1, 2023 is always 7 full months. Likewise, Feb 1 till Jul 31 is always six full months, regardless of leap years.

However, the month count for a given number of days before or after a given date may vary depending both on leap years and on which months are covered by the period exactly. For example, 150 days starting from Jan 1 is May 31, 2022. This period consists of exactly 5 months. However, 150 days from Jan 1, 2024 is May 30, 2024, which is just 4 full months, or 4 months and 30 days to be exact. Such complications do not arise if the period does not include a February, or a leap year. In such cases the same time period in days or weeks always contains the same month count.

    What calendar is used in the month calculator

This calendar month calculator is based on the Gregorian calendar. A solar calendar named after Pope Gregory XIII, it was first introduced in Europe in 1582. Today it sees use in most countries in Europe as well as countries settled or ruled by Europeans during the past centuries such as America. The Gregorian calendar contains 365 days in a typical year and adds an extra day every four years for a total of 366 days to align the calendar with astronomical events related to Earth's rotation around the Sun. Those years are called "leap years".

The Gregorian calendar is used by businesses across the world. In certain jurisdictions it coexists with local calendars.