Like many other time-related websites, this one is also well done, well thought out, and well designed. I find it hard to recall the websites when I need them. This is personal, but unless a website is regularly used, and if I need time to think or look up, I try to go for something on my machine.
The same principle I try to bring up when building something for consumers whose primary objective is something else, and the solution/app is competing with something easy to find, “Can this compete or be faster with pen/paper, or just writing a note to self on WhatsApp?”
The Native Time Apps on macOS are pretty good these days, so I have done away with all sorts of Timezome, Alarm, Timer-related Apps except The Clock.[1]
I think The Clock is just one developer, and I have had the app for as long as I can remember (easily 10+ years). I can do without it and use the native clock to replace most functions, but I like that time slider, which I can use to check the time differences between zones. Settings sync across devices via iCloud. It is just there whenever I need it. It is one of those that you buy once and keep abusing for ages.
1. https://seense.com
