Piday

Mathemagical Calendar

Free

PiDay is the nerdiest calendar app ever made. Every day, PiDay opens to today and shows you exactly where that date appears in the first five billion decimal digits of pi. Search for your birthday, an anniversary, or any date you care about, then see where it lives in infinity. PiDay searches multiple date formats and highlights the best match, so you can explore your date from different calendar conventions and compare where each one appears. Features: Find today’s date in pi instantly Search birthdays, anniversaries, and any other date See the exact position where a date appears Compare multiple date formats Explore a calendar heat map of how early dates appear Save favorite dates Share your discoveries as cards Personalize the app with multiple themes Works on iPhone, iPad, and Mac PiDay keeps things simple: No accounts No ads No tracking A decade worth of bundled dates, or search any string using a live lookup service for dates outside the bundled range. If you’ve ever wondered whether your birthday is hiding in pi, this is the app for you.

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What’s New (1.3 - kim) Non-pi dates use a DDMM or MMDD format to ensure dates are found in these. Celebrations got an upgrade: featured-day popups + confetti now work for Tau Day (6/28), Euler’s Number Day (2/7), Golden Ratio Day (1/6), and World Quantum Day (4/14). Plus a handful of small fixes and polish.

Version 1.3 (kim)

The developer, Erik Veland, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .

  • Data Not Collected

    The developer does not collect any data from this app.

    Privacy practices may vary based, for example, on the features you use or your age. Learn More

    Accessibility

    The developer has not yet indicated which accessibility features this app supports. Learn More

    For more information, visit the developer’s accessibility website .

    Information

    Size
    • 48.3 MB
    Category
    • Education
    Compatibility
    Requires iOS 17.0 or later.
    • iPhone
      Requires iOS 17.0 or later.
    • iPad
      Requires iPadOS 17.0 or later.
    • Mac
      Requires macOS 14.0 or later.
    • Apple Watch
      Requires watchOS 10.0 or later.
    Languages
    • English
    Age Rating
    4+
    Provider
    Erik Veland
    • Erik Veland has identified itself as a trader for this app and confirmed that this product or service complies with European Union law.
    • Address
      22 Hampton St
      East Brisbane Queensland 4169
      Australia
    • Phone Number
      +61 415659045
    • Email
      erik@veland.au
    Copyright
    • © 2026 Erik Veland
  • Developer Website
  • Privacy Policy