Calendar
Week Number Calculator
ISO-8601 week number for a date, and the dates a given week covers.
ISO-8601: week 1 contains the first Thurs…
Also called iso week calculator · what week is it
Date & Time · 7 calculators
Calendar Calculators
Week numbers, day of the year, days left in the year, quarters, months and weeks between dates, and leap years.
Calendar
Day of the Year Calculator
Ordinal day number for a date, and the date for a given day number.
day number = date − 1 January + 1
Also called julian day number · ordinal date calculator
Calendar
Quarter Calculator
Which fiscal or calendar quarter a date falls in, with the quarter’s start and end dates.
quarter = floor(months since the fiscal y…
Also called fiscal quarter calculator · what quarter is it
Calendar
Months Between Dates Calculator
Complete months between two dates, with the leftover days and the decimal months.
Count complete calendar months, then the …
Also called month difference calculator · how many months between
Calendar
Weeks Between Dates Calculator
Weeks between two dates, in whole weeks plus days and as a decimal.
weeks = days ÷ 7
Also called week difference calculator · how many weeks between
Calendar
Add or Subtract Days Calculator
Find the date a number of days, weeks, months or years before or after a given date.
result = start date ± the period given
Also called date plus days · add days to date
Calendar
Leap Year Calculator
Whether a year is a leap year, with the next ones and the rule explained.
leap = (year % 4 = 0 and year % 100 ≠ 0) …
Also called is it a leap year · leap year checker
Key calendar formulas
| Week Number | ISO-8601: week 1 contains the first Thursday of the year |
|---|---|
| Day of the Year | day number = date − 1 January + 1 |
| Quarter | quarter = floor(months since the fiscal year start ÷ 3) + 1 |
| Months Between Dates | Count complete calendar months, then the leftover days |
| Weeks Between Dates | weeks = days ÷ 7 |
| Add or Subtract Days | result = start date ± the period given |
| Leap Year | leap = (year % 4 = 0 and year % 100 ≠ 0) or year % 400 = 0 |