The F91W blog
Know yourF-91W.
Guides, history and care for the watch that never needed a redesign.
01 / guide · 5 min read
How to customize a Casio F-91W: faceplates, negative displays and straps
What you can change on a Casio F-91W, from faceplates and negative displays to leather and nylon straps, what each mod costs and what to watch out for.
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02 / history · 4 Oct 2026
The Casio F-91W: how a 1989 digital watch became an icon
Where the Casio F-91W came from, who designed it, what is inside it, and why a small resin watch from 1989 is still in production.
03 / how-to · 4 Oct 2026
How to set the time on a Casio F-91W (and the alarm, stopwatch and 24-hour mode)
Step-by-step: set the time and date on a Casio F-91W, switch 12/24-hour, set the daily alarm, turn the hourly chime on, and use the stopwatch.
04 / guide · 4 Oct 2026
F-91W vs F-91WB vs F-91WC vs F-91WG: every colourway explained
What the letters after F-91W mean, how the classic, WB, WC and WG versions differ, and how to pick the right colour for you.
05 / care · 4 Oct 2026
Casio F-91W battery: how long it lasts and how to replace it
The F-91W uses a CR2016 cell that Casio rates at about seven years. Here is how to tell it is running low and how to get it replaced safely.
06 / care · 4 Oct 2026
Is the Casio F-91W waterproof? Water resistance and everyday care
What 'water resist' means on a Casio F-91W, what it can and cannot handle, and simple care tips to keep the resin case and strap looking new.
