excel formulas

Converts millisecond epoch format to datetime - https://www.epochconverter.com/
1351108441165 = 10/24/2012 19:54:01
=(A1/ 86400000) + DATE(1970,1,1)


Google Sheets combine date and time into timestamp
=B2+C2
Format as datetime

Time Diff between events
=A3-A2
Format as duration

GoogleSheets epoch conversion
=C1 / 86400 + DATE(1970, 1, 1)


Fuzzy Vlookup on string, checks for N/A and returns blank if N/A, then checks for NOTISBLANK.  If the returned field is NOT BLANK then the field had a value.
Usecase: fuzzy lookup IP in column, check for N/A then look at last scan date to see if client is installed.
=NOT(ISBLANK(IFNA(VLOOKUP("*"&B2&"*",tenable_assets!AN:AV,7,FALSE),)))


Concat & Hyperlink
=HYPERLINK(CONCATENATE("<url_path>", <query_parameter_to_add_from_column>),"<string to display>")


Multi-criteria "database" lookup that will sum a specific column
=DSUM(<database_range>,"column_name_to_sum",{{"column1_name_in_database";<cell_to_match_in_db_column1>},{"column2_name_in_database";"<cell_to_match_in_db_column2>"}})