add schedule

Author: bcumming

docs/guides/gb25.md

@@ -4,6 +4,8 @@ This is temporary documentation for the Gordon Bell second round benchmark runs
 
 ## Schedule
 
+Times are in CEST (Central European  Time): [Time converstion table](https://time.is/compare/0800_18_Aug_2025_in_CET/PT/ET/Perth)
+
 | group  | date | time  | duration (h) | activity |
 | ---    | ---- | ----- | -----------: | --------------------- |
 | -      | 08-18| 08:00 | -            | Daint is reconfigured and resized for GB runs             |