GMTとのタイムゾーンバグ？

[JammyDodger]

以前にも発生したことがあると思います。

Conflict between timezones in "Insert date / time"

I’m afraid the technical reason here is pretty confusing - you can read about it at Moment Timezone | Docs POSIX compatibility requires that the offsets are inverted. Therefore, Etc/GMT-X will have an offset of +X and Etc/GMT+X will have an offset of -X . This is a result of IANA’s Time Zone Database and not an arbitrary choice by Moment.js. Thus, using locality based identifiers is preferred over fixed-offset identifiers. So, in IANA’s Time Zone database, Europe/Oslo is currently equivalent…