Versioning gets better with time. That’s the premise of Calendar Versioning (CalVer), a pragmatic alternative to semantic versioning that aligns software releases with the calendar instead of arbitrary numeric increments. In projects where time matters more than the nature of the change, CalVer brings clarity, predictability, and context.
CalVer is a date-based versioning convention where the version string encodes the release date, typically using combinations of year (YYYY), month (MM), day (DD), and optional modifiers (alpha, rc, dev, etc). This makes version numbers more transparent and easier to interpret at a glance.
Unlike Semantic Versioning, which emphasizes change severity and compatibility, CalVer emphasizes when, making it ideal for:
Projects with frequent, scheduled releases
Systems with long-term support cycles
Projects driven by external timelines (e.g., timezones, security patches)
Uses YY.MM (e.g., 24.04) to align with biannual releases. The version doubles as a support indicator, LTS versions (like 20.04) receive 5 years of updates.
CalVer is not just a versioning format, it's a communication tool. It aligns releases with real-world time, offering immediate context for users, maintainers, and stakeholders. When predictability, release cadence, or support windows are more important than strict compatibility semantics, CalVer excels.
By embedding time directly into your versioning, you simplify lifecycle management, streamline upgrade paths, and build trust through transparency. It's pragmatic, readable, and increasingly adopted across mature, high-impact projects.
FAQs
What is Calendar Versioning (CalVer)?
CalVer is a date-based versioning system where version numbers encode the release date, typically using combinations like year (YYYY), month (MM), or day (DD). It's focused on when software was released, rather than the nature or severity of the changes.
How does CalVer differ from Semantic Versioning (SemVer)?
While SemVer reflects API compatibility and change magnitude (MAJOR.MINOR.PATCH), CalVer reflects release timing. CalVer is better suited for projects with scheduled releases, external timelines, or lifecycle-based support policies.
What are common CalVer formats?
Typical formats include:
YY.MM (e.g., 24.04)
YYYY.MM.PATCH (e.g., 2024.05.2)
YYYYa, YYYYb for unordered releases Modifiers like -alpha, -rc1, or -dev may follow for pre-release versions.
What types of projects benefit most from CalVer?
Operating systems (e.g., Ubuntu)
Frameworks with long-term or time-based support (e.g., Twisted)
Projects impacted by real-world events or policy (e.g., IANA timezone database)
Tools with frequent, cadence-based release cycles
Should my project use CalVer?
Use CalVer if:
Your releases are driven by time, not features
You maintain support windows based on release date
You want users to easily track release recency and lifecycle If compatibility tracking isn’t the priority, CalVer may be a better fit than SemVer.
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