Guides on pregnancy timelines, fertility, age math, working days, calendars and more.https://dateestimator.com/en-ushttps://dateestimator.com/blog/how-to-calculate-pregnancy-due-date/https://dateestimator.com/blog/how-to-calculate-pregnancy-due-date/A step-by-step guide to working out a pregnancy due date with nothing more than a calendar — using Naegele's rule, the LMP method, and the cycle-length adjustment.Sun, 12 Apr 2026 00:00:00 GMTpregnancydue datenaegelehttps://dateestimator.com/blog/fertile-window-explained/https://dateestimator.com/blog/fertile-window-explained/A clear, evidence-grounded explanation of the fertile window, why it's six days long, and how to time it accurately whether you're trying to conceive or trying to avoid it.Wed, 18 Mar 2026 00:00:00 GMTfertilityovulationcyclehttps://dateestimator.com/blog/age-calculation-edge-cases/https://dateestimator.com/blog/age-calculation-edge-cases/Why calculating an exact age in years, months and days is harder than it looks — and the rules our age calculator follows to always produce a consistent answer.Sun, 22 Feb 2026 00:00:00 GMTagecalendarleap yearhttps://dateestimator.com/blog/working-days-explained/https://dateestimator.com/blog/working-days-explained/Counting working days correctly — what counts as a business day, how endpoints are treated, and why holidays vary so widely.Wed, 04 Feb 2026 00:00:00 GMTworking daysbusiness dayslegalhttps://dateestimator.com/blog/multi-calendar-systems-guide/https://dateestimator.com/blog/multi-calendar-systems-guide/An accessible guide to the Gregorian, Hijri, Hebrew, Persian, Buddhist, Japanese and other major calendars — what they have in common and how they differ.Thu, 15 Jan 2026 00:00:00 GMTcalendarhijrihebrewpersianhttps://dateestimator.com/blog/countdown-psychology/https://dateestimator.com/blog/countdown-psychology/How visible countdown timers exploit deadline psychology to improve focus, motivation and follow-through — plus how to use them well.Mon, 08 Dec 2025 00:00:00 GMTcountdownproductivityhabitshttps://dateestimator.com/blog/date-iso-formats/https://dateestimator.com/blog/date-iso-formats/ISO 8601 sorts naturally, eliminates locale ambiguity and prevents off-by-one bugs. Here's why every date you write should look like 2026-05-06.Tue, 21 Oct 2025 00:00:00 GMTiso 8601formatcalendar