Zoho Sheet ISLEAPYEAR Function: Numeric Flags and Calendar Checks
Test date years with explicit date construction, century examples, complete-year totals and clear limits on date validation.
Verification status: See the evidence and test scope described in this guide. How formula examples are checked
ISLEAPYEAR tests the year containing a supplied date. It returns the number 1 for a leap year and 0 otherwise. It does not return the number of days in February, and its documented output is numeric rather than the literal Boolean words TRUE and FALSE.
Availability and verification scope
Zoho’s official ISLEAPYEAR entry was retrieved on October 15, 2026. It documents the rolling web service without establishing an introduction release or a last functioning version; both historical endpoints remain unknown. Current web documentation does not certify mobile or offline-client parity.
The calendar results here were independently calculated from the stated dates. They are reference expectations, not captured native Zoho output. Formulas follow the help’s semicolon notation; check the actual editor’s locale and syntax before pasting them.
Syntax and the kind of input
ISLEAPYEAR(date)
The argument is a date, not a separately labeled year number. For a known year, build a date such as DATE(2024;7;1) and pass that result. Do not assume ISLEAPYEAR(2024) means the year 2024: an unformatted number may be interpreted as a date serial.
The official DATE reference defines its arguments as year, month and day. Using numeric components avoids depending on whether a text date such as 2/5/2024 means February 5 or May 2. This guide displays dates in year-month-day order for clarity; the workbook’s appearance can differ.
Reproduce the stable official examples
Zoho’s text-date examples classify a date in 2020 as 1 and January 1, 2019 as 0. Equivalent explicit-component controls are:
| Formula | Independent expected output |
|---|---|
=ISLEAPYEAR(DATE(2020;12;2)) |
1 |
=ISLEAPYEAR(DATE(2019;1;1)) |
0 |
=ISLEAPYEAR(DATE(2024;1;1)) |
1 |
=ISLEAPYEAR(DATE(2024;12;31)) |
1 |
The first and last day of 2024 give the same classification because the function tests the containing year, not whether the particular day is February 29.
The help also displays ISLEAPYEAR(TODAY()) as 1. That is a time-dependent illustration, not a permanent result. During calendar year 2026 the calendar expectation is 0; during 2028 it is 1. A fixed-date test is more reproducible than TODAY when documenting a result.
Complete century-boundary worksheet
Create LeapYears with Year in A1, Test_date in B1 and Leap_flag in C1. Enter the seven years below in A2:A8. Fill B2 =DATE(A2;7;1) and C2 =ISLEAPYEAR(B2) down to row 8.
| Row | A: year | B: intended date | C: calendar expectation |
|---|---|---|---|
| 2 | 2000 | 2000-07-01 | 1 |
| 3 | 2019 | 2019-07-01 | 0 |
| 4 | 2020 | 2020-07-01 | 1 |
| 5 | 2024 | 2024-07-01 | 1 |
| 6 | 2026 | 2026-07-01 | 0 |
| 7 | 2100 | 2100-07-01 | 0 |
| 8 | 2400 | 2400-07-01 | 1 |
There are four leap flags among the seven examples. The calendar explanation is the Gregorian rule: divisibility by four normally qualifies, except century years must also be divisible by 400. The U.S. Naval Observatory calendar reference supplies that independent rule. The table is a calendar-model cross-check, not native certification of every historical date serial.
Advanced: derive an explicit year-length field
Put Days_in_year in D1 and fill D2 =365+C2 through D8. The expected results are 366,365,366,366,365,365,366. This calculation uses the documented numeric flag directly.
If a planning model assigns one unit to each calendar day of a complete year, that is the corresponding annual count. It is not the count of working days, weekdays or eligible billing days. Holidays and partial-year boundaries need their own rules.
For another complete interval list 2024,2025,2026,2027,2028 in F2:F6 and compute =365+ISLEAPYEAR(DATE(F2;1;1)) in G2, filled down. The expected total is 1827 days, from three ordinary years and two leap years. This concerns all five complete calendar years, not an inclusive count of two endpoint dates.
Advanced: avoid mistaking normalization for validation
DATE can normalize an overflowing day into the following month. Consequently, building an impossible February date and then applying ISLEAPYEAR does not validate the original day/month combination. The function sees the resulting date and classifies its year.
For example, DATE(2023;2;29) normalizes to March 1, 2023 under Zoho’s documented overflow rule; ISLEAPYEAR still returns the calendar expectation 0. Validate the original components separately if rejecting impossible dates is the purpose.
Errors and troubleshooting
The function entry supplies shared name, type and reference errors, but no detailed serial-date domain, blank-coercion or invalid-text matrix. Its generic lookup-error explanation should not be treated as an ISLEAPYEAR-specific lookup rule.
If a familiar year produces an unexpected result, inspect whether the input is a date, a raw number or text. If only appearance differs, check the date format. If a TODAY-based result changed between saved examples, check the year before assuming the formula changed. No exact native error or complete historical-calendar behavior is asserted beyond the checked documentation.