[mrighele]

It is not good enough. All the major browsers that I tried do not properly handle the timezone offset, as I discovered a few days ago (I put a more complete answer about this in a stackoverflow answer, but I don't know if putting the link would count as self-promotion so I will leave it out)

In short, the ES5 specs [1] say that

    The implementation of ECMAScript should not try to determine whether the 
    exact time was subject to daylight saving time, but just whether daylight 
    saving time would have been in effect if the current daylight saving time 
    algorithm had been used at the time. This avoids complications such as 
    taking into account the years that the locale observed daylight saving time year round.

This means that if your country handled daylight saving differently in the past, converting the timestamp to string may give you a wrong answer (this would be the case of a number of european countries during WWII).

The spec has been improved starting with ES6 [2], but to my knowledge no browser has fixed the issue:

    An implementation dependent algorithm using best available information on 
    time zones to determine the local daylight saving time adjustment 
    DaylightSavingTA(t), measured in milliseconds. An implementation of 
    ECMAScript is expected to make its best effort to determine the local 
    daylight saving time adjustment.

    NOTE It is recommended that implementations use the 
    time zone information of the IANA Time Zone Database 
    http://www.iana.org/time-zones/.

A solution is to use a JS library that has its own timezone database.

[1] http://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.8 [2] http://www.ecma-international.org/ecma-262/6.0/#sec-daylight...

[mirekrusin]

It's good enough (and correct) to store unix timestamps. For displaying the date - your comment applies...

Unix timestamp refers unambiguously to single point in time. Interpretation of this point in time in different timezones is complicated but it's outside of it.

[mrighele]

I agree that storing unix timestamps is a good approach.

My issue was with "then displayed to the proper locale by the client's device." I mean, by itself it is ok, but in the case of a web client one cannot unfortunately just use the Date object and convert the timestamp to a human readable string.