Quarter of the YearFree online date & time calculator — instant results, no sign-up
Find which calendar quarter a date falls in.
Sign in to save results and favorites.
About the Quarter of the Year
The Quarter of the Year calculator identifies the calendar quarter containing a selected date and shows that quarter’s first and last dates. For the default date, 2026-10-23, it returns Q4 2026, running from Thu, October 1, 2026 through Thu, December 31, 2026.
- Date
- The calendar date to classify, entered as year-month-day (YYYY-MM-DD), with a default of 2026-10-23 and precision of one day.
Formula and method
q = floor((m − 1) / 3) + 1; s = 3(q − 1) + 1; e = 3q; S = date(y, s, 1); E = date(y, e, daysInMonth(y, e)). The quarter label is Qq y. For 2026-10-23: q = floor((10 − 1) / 3) + 1 = 4, S = 2026-10-01, and E = 2026-12-31.
- yThe year of the input date: 2026 for the default input.
- mThe input month number, from 1 for January through 12 for December: 10 for the default input.
- qThe calendar quarter number, from 1 through 4.
- sThe first month number of the quarter.
- eThe last month number of the quarter.
- SThe quarter’s first calendar date.
- EThe quarter’s last calendar date.
- floor(x)The greatest integer less than or equal to x.
- date(y, m, d)A calendar date constructed from year y, month m, and day d.
- daysInMonth(y, m)The number of calendar days in month m of year y.
Extract the year and month from the date, then group the month into one of four three-month periods: January–March, April–June, July–September, or October–December. Calculate the first and last months of that quarter, set its start to the first day of the first month, and set its end to the last day of the last month. Format both boundary dates with their weekdays. For 2026-10-23, October belongs to Q4, so the result is Q4 2026 with boundaries Thu, October 1, 2026 and Thu, December 31, 2026.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Date1970-01-01
Results
- QuarterQ1 1970
- Quarter startsThu, January 1, 1970
- Quarter endsTue, March 31, 1970
How to use the Quarter of the Year
- 1Enter or select the date in the Date field; keep 2026-10-23 to reproduce the default example.
- 2Run the calculation, or read the updated result if the page calculates automatically.
- 3Read Quarter: the default date returns Q4 2026.
- 4Read Quarter starts: the default result is Thu, October 1, 2026.
- 5Read Quarter ends: the default result is Thu, December 31, 2026.
Reading your result
Quarter gives the quarter number and calendar year containing your date: Q4 2026 means October through December of 2026. Quarter starts gives the first included date, Thu, October 1, 2026. Quarter ends gives the last included date, Thu, December 31, 2026. Both boundary dates belong to the quarter, and Thu indicates Thursday.
Limitations
This tool assumes the Gregorian calendar and standard calendar quarters beginning in January, April, July, and October. It does not calculate custom fiscal quarters, retail reporting periods, business-day boundaries, or tax deadlines. It classifies a date rather than a timestamp, so time of day and time-zone conversion are outside its scope. Quarter boundaries remain calendar dates even when they fall on weekends or holidays.
Common questions
Why does 2026-10-23 fall in Q4 2026?+
October is month 10, and Q4 covers October, November, and December. The quarter label retains the input date’s year, giving Q4 2026.
Are the quarter’s start and end dates included?+
Yes. Q4 2026 includes both Thu, October 1, 2026 and Thu, December 31, 2026, as well as every date between them.
Can this calculator identify my company’s fiscal quarter?+
Only if your company uses the same quarter periods and year labels as the calendar year. The calculator has no fiscal-year-start input, so it cannot adjust for a different fiscal calendar.
Does a leap year change which quarter a date belongs to?+
No. Quarter membership depends on the month, not the number of days in the year. A leap day belongs to Q1, but the standard quarter boundary months remain unchanged.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
You might also like
Date Difference
Count the days, weeks and months between two dates.
Add Days to a Date
Find the date a number of days from a starting date.
Day of the Week
Find out which day of the week any date falls on.
Week Number
Find the ISO week number of any date.
Day of the Year
See which day of the year a date is, and how many days remain.
Leap Year Checker
Check whether any year is a leap year.
Results are estimates for informational purposes and are not financial, medical or legal advice.