Then I started looking more closely at how calendar interfaces actually work, and the "simple grid" turned into a surprisingly interesting engineering problem.
Here are the things that surprised me most. A calendar date is not necessarily a timestamp
But JavaScript's Date represents a point on a timeline. A calendar date and an instant in time are not always the same concept.
This distinction becomes especially important when the same interface needs to work across locations.
For date-only data, adding a timezone too early can create problems instead of solving them. Separate calendar math from presentation
Another thing I learned quickly: don't make one function responsible for everything.
It can feed: a desktop calendar a mobile calendar a yearly overview a printable page a PDF generator
The boring architecture turned out to be the useful architecture. A month grid is mostly an offset problem
A fixed grid can also prevent the interface from jumping vertically when someone moves from one month to another.
Small detail, better experience. Sunday-first and Monday-first should be configuration
The rendering layer doesn't need to understand why the week begins on a particular day.
Regional behavior should usually be configuration, not architecture. Don't hard-code what the platform already knows
Now localization belongs to the presentation layer rather than the calendar engine.
That separation becomes increasingly valuable as the project grows. CSS Grid makes the visual part surprisingly straightforward
Once the data model is correct, the basic seven-column interface is almost boring:
The data does not know whether it is being displayed in one column or twelve. Print is a completely different medium
This has been one of the more interesting problems for me while working with calendar resources at JW Calendar.
For a static calendar, table semantics can sometimes express those relationships naturally: