Last Day of Month Calculator

How month-end math works in seconds: Select a month and year and the tool applies the day-zero trick, constructing day zero of the following month to land exactly on the current month final day. Results show the ISO date plus the weekday name with leap-year February handled automatically. Answers appear in seconds at $0 cost with all logic local. Austin accountants closing $40,000 books confirm 02/28/2026 instantly. Day-zero logic nails 02/28/2026 for $40,000 book closes.

Reading dates, weekdays, and leap years: The headline pairs month and year with the resolved date like 2026-02-28 plus Saturday-style weekday labels for scheduling. Century rules apply correctly, so 2024 February yields 29 while 2026 yields 28. A Chicago payroll team processing $120,000 runs on 08/31/2026 verifies payday weekday before submitting. Denver gyms billing $9,000 cycles align charges to actual ends. Weekday labels keep $120,000 payroll submissions on schedule.

Billing close, payroll, and reporting cycles: Finance calendars hinge on true month ends rather than assumed 30th dates that drift quarterly. A Miami hotel reconciling $65,000 folios closes February correctly without carrying balances. A Seattle SaaS team renewing $30,000 subscriptions dated 08/20/2026 prorates trials to exact ends. A New York auditor locking $500,000 quarterly closes rolls January through March without spillover. True ends stop $65,000 folio balances from drifting monthly.

Scheduling quirks and weekend ends: When month end lands on weekends or holidays, pair the true date with business-day rules to pick the observed close or pay date. February swings between 28 and 29 days, while April, June, September, and November always end on the 30th. Denver planners shift $7,000 retainer deadlines forward when the 31st falls on Sunday. Observed-date rules move $7,000 retainers off weekends cleanly.

Automation habits and dated records: Store outputs like close-02-28-2026 in runbooks so reconciliations repeat identically across staff rotations. Validate every quarter before locking payroll calendars, since one wrong February cascades across reports. Reusable lookups beat spreadsheet formulas that hardcode 30-day assumptions and break each February. Runbook dates like close-02-28-2026 standardize $500,000 audits.

Privacy and local browser execution: Everything computes locally in your browser with no uploads or accounts, safe for payroll calendars. The tool is free with no signup required ever. Reopen before 09/01/2026 closes, recheck leap years, and pair with days-in-month tools from Austin to New York. Leap rechecks before 09/01/2026 closes prevent February cascades. Denver vendors validate $45,000 calendars monthly while Austin landlords prorate $2,200 leases exactly.