Time in programming can be annoying. This would be even harder, JScript is not the biggest language, but I bet it can take your local time. Then using your local time you could sniff your contact's ip address and their location and match their location to their timezone. But that won't be accurate because sniffing ip addresses is not that easy, and they maybe using a proxy, and their location may not match their timezone. Then you need to think about daylight savings, which could be near impossible to check. Then once you get your contact's time, you need to replace the messages they say with the correct time. Like if they say, "see you at 9", or "9:15 it is then", you won't know how to detect when they mention time. So basically without me blabbing on even more, this script is near impossible, but possible, just expect tons and tons of limitations.
The best way like said earlier is for Messenger to add the feature itself
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