casual-timezones cannot work under Termux on Android because tzdata is not packaged, by design

[gnomon-]

The casual-timezone-zone-info-database defvar expects to be able to be pointed at a tzdata.zi file, by default at /usr/share/zoneinfo/tzdata.zi, which awk can process.

Unfortunately under Android both this location and this format are not included, which means emacs running under Termux cannot use casual-timezone in the way it is currently designed. Furthermore Termux has stated their intention to not package tzdata, with a well-reasoned position, so this gap is unlikely to be plugged in the short term.

This challenge also affects other packages which depend on directly accessing tzdata files, e.g. the tzc emacs package (cf. issue 6).

In theory it should be possible to install the tzdata files someplace in my Termux home directory outside of the Termux packaging framework and customize my init to point casual-timezones there; I'll report back if I get this working in a reasonable way.