Adding overlay to timechart

[ILLLLM]

source=*.log host=myhostname "provider=microsoft" "status=SENT_TO_AGENT" | timechart dedup_splitvals=t limit=10 useother=t count AS "Count of Event Object" by provider format=$VAL$:::$AGG$ | fields + _time, "*"

This will display a count of entries in the logs that say "SENT_TO_AGENT"

I want to display an average line chart for previous 3 months, and the current month as an overlay over the previous months. 

[ITWhisperer]

What does your timechart currently give you? Daily counts, hourly counts? What does "average" mean in this context? Does previous 3 months include the current month or only complete months prior to the current month?

Please provide some sample representative anonymised events and a representation of what your output results would be (as a table not a graph).