After Mary's answer, I played around with this a bit more and voila:
index=SomeIndex earliest=10/23/2019:12:00:00 latest=10/28/2019:12:00:00
| eval UserLower=lower(User)
| timechart count by UserLower
| rename UserLower as "User ID"
**| eval timeOffset=strftime(_time, "%:::z")
| eval _time=strftime(_time - 60*60*timeOffset, "%Y-%m-%dT%H:%M:%SZ")**
Conclusion: You need to evaluate your readable date format (whatever that is) on top of the _time field only AFTER you have asked splunk to produce the timechart using the original _time field (which holds the time in Unix time format just the way splunk likes it).
Please feel free to comment and suggest more elegant/appropriate solutions.
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