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DateAndTimePro.com uses transparent, internationally recognized calendar conventions. This page summarizes them so users can interpret results consistently.
Gregorian calendar assumptions
- All default calculations use the proleptic Gregorian calendar.
- Date ranges before the historical adoption of the Gregorian calendar are interpreted using the same rules to ensure mathematical consistency.
- Non-Gregorian calendars are explicitly labeled where supported.
ISO 8601 date conventions
- Dates are stored and exchanged internally in ISO 8601 format (YYYY-MM-DD).
- Display formats are localized to user preference where applicable but remain unambiguous in source data.
- Time strings follow 24-hour ISO conventions internally and may be displayed in 12-hour format on output.
Week numbering
- Default week numbering follows ISO 8601: weeks begin on Monday and week 1 contains the first Thursday of the year.
- Some calculators support alternative week-start days (Sunday or Saturday) where culturally relevant.
Recurring calculations
- Recurrence patterns (weekly, monthly, yearly) anchor to the original date and roll forward according to the selected interval.
- Monthly recurrences that fall on a non-existent day (e.g., the 31st of February) roll to the last day of the month.
- Business-day recurrences skip Saturdays and Sundays by default and can be adjusted for regional weekend conventions where supported.
Supported calendar systems
The platform's primary surface is Gregorian. Selected guides and countdowns reference additional calendars (such as lunar calendars for holidays like Diwali or Easter) using authoritative public reference data. These references are educational and should be verified against official sources for liturgical or legal use.
Published by Relationale LLC, founded by Keiron Brown. For questions about this document, see our Contact page or browse the Time Intelligence Trust Center.