For anyone having this issue, add a EN_US locale string to the URL.  Eg   ...../vsphere-client/?locale=EN_US   The schedules will now be able to be edited correctly.  Here's hoping for a permanent fix in the next major release.
Hi, Has anyone got a fix for the region problem relating to the scheduling? When trying to add or edit a schedule, we get the following error. Title: Too SmallText: startTime does not meet the minimum value of 0 From what another user said it was impacting non US customers and the workaround was to change region of the computer you were using. I've tried this and it doesn't work. This error is now a few years old.  
Virtual Storage Manager - startTime does not meet the minimum value of 0 error