Next occurrence of a weekday

What next-weekday means and what the response contains

Finding the next occurrence of a weekday answers a different question from counting business days or formatting locale strings: it walks forward on the Gregorian civil calendar, one midnight at a time, until the target named day of week is reached, without skipping holidays or depending on the local week-start convention. You supply a base date as a strict YYYY-MM-DD string and a weekday field with an English full name such as Monday or a common abbreviation such as Mon, Fri, or Thu; the engine normalizes case and token form against a fixed map and rejects anything it does not recognize. If you need business-day offsets, epoch conversion, multi-format parsing, or ISO week numbers, use those dedicated tools; this page answers only the soonest on-or-after Gregorian date for a named weekday. On-or-after semantics mean that if the base already lands on the requested weekday, days_until is zero and result equals the base date; otherwise days_until is the whole-day distance from one through six to the next matching day. The calculator returns the normalized base date, the canonical weekday name used, the result ISO string, days_until, the base weekday name and ISO weekday number Monday equals one through Sunday equals seven, the same pair for the result, the result year month and day fields, the base components for easy piping, and a short formula reminder. Rejected cases include a missing date or weekday field, wrong shapes such as 2024/03/15, impossible months, days that do not exist such as 2023-02-29, and unrecognized weekday strings such as Funday or numeric codes.

How the date and weekday are read and how the result stays reproducible

The string must match four digits, a hyphen, two digits, another hyphen, and two digits; leading or trailing spaces are trimmed, but partial dates, ordinal day-of-year alone, and month names are not expanded here. After parsing, the year must fall between 1 and 9999, the month between 1 and 12, and the day between 1 and the true length of that month in that year, with leap years following the Gregorian rule of divisible by four except century years not divisible by four hundred. The preferred base field is date, but aliases iso_date, d, value, base, and from are accepted so spreadsheets, query strings, and typed forms can reuse the same contract without renaming columns. The weekday field, with aliases day, dow, target, and target_weekday, must be an English full name or a common abbreviation from the documented set; tokens are lowercased and looked up in a static map from Sunday through Saturday, while pure numbers and invented labels are rejected with a clear message so a bad cell does not become a wrong next day. Internally the engine obtains the base day of week with Sakamoto pure-integer arithmetic, computes days_until as the modular distance to the target on a seven-day cycle, converts the civil triple to a proleptic Gregorian serial day count using the well-known days_from_civil mapping, adds the integer offset, then recovers year, month, and day with civil_from_days. Pair the free browser run on this page with the priced API when you need the identical next weekday inside an automated pipeline.

Where next-weekday arithmetic fits in scheduling, planning, and software

On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the KIT tier-A catalog and lets you move from a one-off check to a pipeline without changing the mathematical result.