DateTime picker returns inconsistent timezone and non-ISO formatted values

[ryanhamilton]

user-sl user-mpm

The DateTime picker has multiple issues related to formatting and timezone handling.

Problems:

• Single DateTime values do not include seconds (SS) in the output.
• The timezone used by the picker is fixed at component creation time and does not update if the user later changes the timezone.
• This behavior is confusing and inconsistent with user expectations.

Requested improvements:

1. Single DateTime should return ISO format: YYYY-MM-DD HH:MM:SS (with seconds populated, e.g. :00)
2. Timezone should reflect the currently selected timezone at the time of selection
3. UI behavior could follow Grafana’s approach, which clearly displays the active timezone in the time selector

Priority: VERY HIGH