PerfectCalendar is a pure C / Win32 API taskbar calendar that boots silently to the system tray and weighs ~230 KB on disk — no .NET, no WebView2, no background sync daemon.
Key features: • Flat-file event scheduling (events.dat — plain text, always yours) • MCM_SETDAYSTATE bitmask highlighting — days with events appear bold • Wildcard recurring events: ****-12-25 (yearly), ****-**-01 (monthly) • Global hotkey (Ctrl+Shift+Space default) — summons to your cursor • Conflict-safe hotkey: shows tray notification instead of crashing • Idle fade transparency via WS_EX_LAYERED • ISO week-number column (MCS_WEEKNUMBERS) • Multi-format date copy (ISO 8601, US, long form) • UTC clock alongside local time • HiDPI / 4K aware, mouse-wheel font zoom • Explorer crash resilience (TaskbarCreated) • All settings persisted to HKCU registry
Publisher’s description
What is PerfectCalendar?
PerfectCalendar is an open-source project management program for Windows from Gsasl. It is written in C.
Installation and requirements
Official installers exist for 64-bit as Portable. It runs without installation (portable). It needs Windows 10 1809 or newer.
Updates and version history
The current version is 1.3.0, released on April 2, 2026. 2 versions are listed since April 2, 2026, each with links to its own installer files.
Project description on GitHub: “Clean, open-source, lightweight alternatives to bloated Windows features and apps. (Built in pure C with the native Win32 API. for most )”
Pros / Cons
Pros
- Open source: the code can be inspected and built by anyone
- Portable: runs without installation
Cons
- No native ARM64 build
In short: PerfectCalendar is an open-source project management tool for 64-bit PCs.
Is PerfectCalendar safe to download?
- The file is served by github.com, the publisher’s own domain
- The download link uses HTTPS
- A SHA256 hash is published, so you can verify the file:
D93B8356FA3A01A2EA7CFC90436DB13E5CB3A62831DD7DD69E4FED59C840B363· Open the VirusTotal report for this hash - The link has not been checked yet
- The source code is public
- ExeAtlas does not host, wrap or modify installers
Related guide: How to check a file’s SHA256 hash on Windows
Recent versions
All 2 versions ›| Version | Date | Size | Files |
|---|---|---|---|
| 1.3.0Latest | April 2, 2026 | — | 64-bit Portable |
| 1.1.0 | April 2, 2026 | — | 64-bit Portable |
Install from the command line
Silent install ›winget install --id Gsasl.PerfectCalendar -eProgram files (.exe): perfectcalendar.exe
Related guide: How to use winget: install and update apps
Information
- Publisher
- Gsasl
- Category
- Project management
- Licence
- MIT
- Price
- Free
- Source code
- github.com/Gsasl/WinOptimizer_exe
- Written in
- C
- Requires
- Windows 11 / 10 (Windows 10 1809+)
- Architecture
- 64-bit
- Installer
- Portable
- Version
- 1.3.0
- Released
- April 2, 2026
- Added to the catalogue
- April 2, 2026
- Versions listed
- 2
- Website
- github.com
- winget ID
- Gsasl.PerfectCalendar
Ratings and reviews
No reviews yet. Be the first to rate it.
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Frequently asked questions
Is PerfectCalendar free?
Yes. PerfectCalendar is open-source software under the MIT licence.
Is PerfectCalendar safe to download?
The download comes from github.com, which belongs to the publisher; ExeAtlas does not host or change the file. Compare its SHA256 hash with the one shown here, or open the VirusTotal report for that hash.
How do I install PerfectCalendar with winget?
Open PowerShell or Windows Terminal and run the winget command shown on this page. winget downloads the official installer and checks its SHA256 hash before running it.
Which Windows versions does PerfectCalendar support?
The installer requires Windows 10 1809 or newer and is available for 64-bit.
Does PerfectCalendar run on ARM (Windows on Arm)?
There is no ARM64 build; Windows 11 on Arm can run the 64-bit version through emulation.
Where can I download an older version of PerfectCalendar?
The versions page lists all 2 versions with links to their official installer files, back to April 2, 2026.
Can I use PerfectCalendar without administrator rights?
Yes, it is portable: unpack and run it.
What are alternatives to PerfectCalendar?
GanttProject, XrmToolBox, Todoist, t-clock and Cal. The alternatives page compares them.
