Methodology

Main Page Types

Most pages on the site fall into six groups: relative date pages, business-day pages, calendar pages, ISO week pages, time zone pages, and date-format reference pages.

Each group uses a declared rule. Calendar-day pages include weekends. Business-day pages currently skip Saturdays and Sundays. ISO week pages use Monday-start ISO rules. Time zone pages use IANA time zone identifiers.

How Relative Dates Are Built

Relative date pages start from the local calendar date used at render time, then add or subtract the requested number of calendar days, weeks, or months.

From-date pages use an explicit YYYY-MM-DD start date in the URL. Those pages are evergreen because the start date does not depend on the day the page is crawled or read.

Week pages use seven calendar days per week. Month pages add calendar months and clamp to the final valid day when the target month is shorter.

How Business Days Are Built

Business-day pages move forward one calendar day at a time and count only Monday through Friday.

The first version does not remove country-specific public holidays. Pages that use this rule state the limitation clearly so weekday counts are not mistaken for official local deadline calculations.

How Time Zones Are Built

Time zone pages compare cities by converting the same UTC instant into each city's IANA time zone identifier.

This lets each comparison follow daylight saving transitions for the selected locations.

Abbreviation pages are treated differently from city pages. When an abbreviation such as EST, CET, or PST is ambiguous, Date Time Encyclopedia shows the fixed offset or reference basis used for that lookup.

How Evergreen Wording Is Handled

Date-offset pages are written around the current calendar date used for the rendered page. Time-zone pages state the time difference or daylight-saving range instead of pretending every location has one fixed answer all year.

Fixed from-date pages use the start date in the URL and do not need to change when today's date changes.

What Consistency Means On This Site

A lookup is considered internally consistent when the title, direct answer, summary table, method text, FAQ, and related links all reflect the same calendar or time zone rule.

Consistency does not mean that every answer is universally official. It means the rule is explicit and applied cleanly from top to bottom.