How to Calculate Months Between Dates: A Step-by-Step Guide

Updated 5 Oct 2026 in Date & Time

Counts complete calendar months between two dates.

Dates and durations matter for notice periods, leave planning, project deadlines and contracts. Counting days on a calendar is slow and easy to get wrong, especially across months of different lengths.

What you need

• Start date
• End date

Step by step

1. Enter the start date.
2. Enter the end date.
3. The results update as you type, or press Calculate.
4. Read the complete months first, then the supporting figures below it.

The formula

Months = year difference × 12 + month difference, minus 1 if the end day is earlier.

Worked example

For example, with these inputs:

• Start date: 15 Mar 2024
• End date: 5 Oct 2026

the calculator returns:

• Complete months: 30 months

Practical tips

• Notice periods in employment contracts may be counted in calendar days or working days, so read the wording carefully.
• Convert times to minutes before subtracting, then convert back to hours and minutes.
• Public holidays are not weekends; subtract them separately when counting working days.
• For overnight shifts, add 24 hours when the end time is earlier than the start time.

Background

Singapore has 11 gazetted public holidays a year, and when one falls on a Sunday the following Monday is a holiday. Working-day calculations therefore need holidays removed separately from weekends.

When sharing dates internationally, write the month as a word to avoid confusion between day-month and month-day formats.

Time durations are easier to handle in minutes. Convert each time to minutes after midnight, subtract, then convert back to hours and minutes, adding 24 hours for shifts that run past midnight.

Related calculations

• Age Calculator: Calculates exact age in years, months and days.
• Days Between Dates Calculator: Counts days between two dates.
• Add Days to a Date Calculator: Finds the date a number of days after another date.
• Subtract Days from a Date Calculator: Finds the date a number of days before another date.

Want to skip the arithmetic? The free Months Between Dates Calculator does all of this instantly and updates as you type.

Run your own numbers: Months Between Dates Calculator