Timestamps provided in Sigfox API are displayed in EPOCH time format and in UTC time. Therefore API time might differ from a customer's own timezone.
This is not customizable and users are advised to take this into account when using API timestamps.
You may find more information about EPOCH here: https://en.wikipedia.org/wiki/Epoch_(reference_date)
Conversion is also possible through multiple website such as: www.epochconverter.com