DayCalcy

A simple, private, and completely offline date calculator and reminder app for Android. Free and open-source software licensed under GNU GPL v3.0.

Features DayCalcy includes:

Age Calculator — Calculate exact age, including age at a selected date and next-birthday information. Date Difference — Calculate the difference between two dates, with an option to include the end date. Add / Subtract Date — Add or subtract years, months, weeks, days, and business days from a date. Day Counter — Count days between dates, including business-day mode and holiday handling. Day of Week — Find the weekday for any date. Date Reminder — Create one-time and yearly recurring reminders with local notifications. Calendar — Browse dates, reminders, history markers, and yearly reminders. History — Automatically save recent calculation results locally, with filters, grouping, reopening, and deletion. Year Progress — View progress through the selected year. Widgets — Home-screen countdown widgets in 2×2 and 4×2 sizes. Theme Support — System, Light, and Dark theme modes. Calculators Age Calculator Exact age in years, months, and days. Calculate age at a selected date. Next birthday countdown and weekday information. Date Difference Calculate the difference between two dates. Optional include-end-date calculation. Business-day calculations. Custom holiday support. Add / Subtract Date Add or subtract years, months, weeks, and days. Business-day mode with holiday handling. Day Counter Count days between selected dates. Business-day mode. Custom holiday support. Day of Week Find the weekday for any date. Includes useful date information such as day of year, ISO week, and days remaining in the year. Calendar & Reminders Select any date from the calendar without automatically opening a reminder. View reminders and other date information for the selected date. Calendar markers distinguish History, one-time reminders, and yearly reminders. Yearly reminders appear on the same month and day each year. Tap a reminder item to open the corresponding reminder in Date Reminder. Returning from a reminder preserves the Calendar state. Multiple reminders can be shown for the same date. Reminder notifications work locally on the device. Reminder actions include Done and Snooze. Deleted reminders cancel their already-posted notifications. Reminder scheduling includes exact-alarm handling with an inexact fallback when exact alarms are unavailable. Reminders are restored and rescheduled after relevant device time, timezone, and reboot events. When opening a specific reminder from Calendar, Date Reminder automatically scrolls to it and briefly highlights it with a soft theme-aware color. History Calculation results can be saved automatically to local history.

Recent calculations are stored on the device. Filters and grouping make saved calculations easier to browse. Open a history entry to view the exact calculation again. Individual entries can be deleted. History is limited to the most recent 100 entries. History does not continuously save Year Progress screens. Year Progress View progress through the selected year. Calendar Information can show Year Progress for the selected date. Year Progress notifications and widget support are available. Widgets 2×2 countdown widget. 4×2 wide countdown widget. Multiple widget instances can use different saved reminders/dates. Countdown information updates locally. Progress ring support. Light and Dark widget appearance follows the DayCalcy theme. Widgets remain completely offline. Results & Sharing Copy the complete calculation result with one Copy action. Share the complete calculation result with one Share action. Actions are shown once for the complete result rather than repeated on every result section. Offline & Privacy DayCalcy works completely offline.

No internet connection is required. No online APIs or remote services are used. No analytics or account is required. Calculations, reminders, history, and settings stay on the device. The app is designed to work without network access. Other System, Light, and Dark themes. About section with Changelog. Local reminder notifications. Simple and lightweight interface.