An ‘epoch’ is the Unix ‘time zero’, also a synonym of the ‘Unix time’. AMPScript time&date functions don’t support Unix timestamp format and require a human-format such as ISO 8601. To convert a timestamp to a date format, simply use the SSJS to create a new Date object…
Convert Epoch to ISO for AMPScript
Create a Date object for the original timestamp as follows:
<script runat="server">
Platform.Load("core","1");
var originalTimeStamp = Attribute.GetValue("originalTimeStamp");
var myTimeStamp = new Date(originalTimaStamp);
Variable.SetValue("@timeStamp", myTimeStamp);
</script>
Format ISO Timestamp Using AMPScript
The FormatDate() function is useful to localize the timestamp in a very elegant way:
SET @locale = AttributeValue("Locale")
SET @timeStampLong = FormatDate(@timeStamp,"l")
SET @timeStampLocalized = FormatDate(@timeStamp,"l","s",@locale)
Trouble with a Time Offset in AMPScript
The ISO timestamp format provides an offset value related to the UTC (Z as the Zulu time means zero offset). If the offset is “+02:00,” it means that the local time is 2 hours ahead of UTC. If the offset is “-05:30,” it means that the local time is 5 hours and 30 minutes behind UTC. The offset is an essential part of the ISO 8601 format because it allows you to specify the exact time zone in which a date and time are expressed, making it easy to convert and compare times across different time zones accurately. Passing a timestamp with an offset to the FormatDate() function returns the time in UTC! Trying to calculate the offset using the getTimeZoneOffset() JavaScript function complicates the things further, as the local time is the SFMC server time that is UTC-6. Interestingly enough a web version of an email (VAWP) may vary further if a browser local settings are used for calculations… To format and show the local time I simply trimmed the offset part.