As a long time developer of FileMaker solutions, I clearly remember the first time I personally attempted to create a calendar solution. It was not as easy as I'd initially thought. There were a TON of "little things" which you find out about down the road.
Don't get me wrong, the learning experience is well worth it and made me a better developer for sure! But, when it comes to building one natively within FileMaker today, it just doesn't make much sense. That is, unless you really only need the most basic of calendars. If you don't care about multiple calendars, flexible displays and interaction, the ability to drag-n-drop and many more features then, sure, you can make a grid of 42 objects and show "some" of your solution data.
However, if you're in the need of something which will handle user editing controls, multiple time zones, multiple view styles and is HIGHLY extensible, then you can't beat free if you're willing to take the time and learn about FullCalendar.
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