# Appointment Slot UTC?

**URL:** <https://developer.community.nhs.uk/t/appointment-slot-utc/15151>\
**Category:** e-Referral Service FHIR API\
**Created:** [18 September 2026 13:08 UTC](https://developer.community.nhs.uk/t/appointment-slot-utc/15151 "2026-09-18T13:08:50Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![hayward](https://avatars.discourse-cdn.com/v4/letter/h/b9e5f3/32.png) [@hayward](https://developer.community.nhs.uk/u/hayward)\
**Post date:** [18 September 2026 13:08 UTC](https://developer.community.nhs.uk/t/appointment-slot-utc/15151/1 "2026-09-18T13:08:50Z")

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Afternoon.

The ERS spec doesn’t seem to clearly indicate if the start and end times for an appointment are returned in UTC or not?

The spec purely says :  
**start: date-time  
required**

**end: date-time  
required**

The data retrieved when requesting slots comes over as something like:

“start”: “2026-09-20T10:40”,  
“end”: “2026-09-20T10:59:00”,

Those times aren’t indicative either way? Having moved some test servers to a different timezone, we are having some issues and want to get clarity on how to best handle that.

Does this mean the appointment is at 10:40 UK time ? Or 11:40 UK time (if UK is +1) etc.

This leads to the follow up question : when booking the appointment, we’ve now hit an error stating the time returned for the slot doesn’t match. If we assume it is 10:40 UTC , and we return 11:40+1 I can understand the mismatch.

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**Author:** ![zubeir.tai](https://dub1.discourse-cdn.com/nhsdigitaldeveloper/user_avatar/developer.community.nhs.uk/zubeir.tai/32/413_2.png) [@zubeir.tai](https://developer.community.nhs.uk/u/zubeir.tai)\
**Post date:** [18 September 2026 13:31 UTC](https://developer.community.nhs.uk/t/appointment-slot-utc/15151/2 "2026-09-18T13:31:43Z")

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Hi @hayward - The start and end date time of the Slot will always be indicated to be UTC.