UTCModDate.txt

## Modification Timestamp : UTCModeDate

included as a column in most (all ?) tables

uses SQlite function julianday with argument 'now' to generate a timestamp in the  UTC JulianDay format. This is not what RM uses, however.
RM subtracts an offset:

julianday('now') - 2415018.5

This generates a "modified Julian Date'

Modified Julian Date means there is an offset subtracted from the standard Julian Date number.
Usually, this offset is: 2400000.5 but RM uses Microsoft's offset: 2415018.5
see:
[UTCModDate.txt](https://github.com/ricko2001/RootsMagic_Database_Design/blob/main/UTCModDate.txt)\
<https://en.wikipedia.org/wiki/Julian_day>\
<https://answers.microsoft.com/en-us/msoffice/forum/all/julian-date/7d23f252-272a-4e52-802e-ec3f3e616845>
<https://answers.microsoft.com/en-us/msoffice/forum/all/julian-date/7d23f252-272a-4e52-802e-ec3f3e616845>


Microsoft uses days since Dec20 1899.

Julian date is from 

offset      start point                name
0           noon January 1, 4713 BC   Original Julian Date. No controversy.
2400000.5   midnight Nov. 17 1858     more standard Modified JD offset
2415018.5   midnight Dec. 30, 1899    Microsoft MJD offset  
2430000.0   midnight Jan. 5, 1941     some astrophysicists use this


https://stackoverflow.com/questions/5248827/convert-datetime-to-julian-date-in-c-sharp-tooadate-safe


SQLite docs
https://www.sqlite.org/lang_datefunc.html

using SQLite-
``` SQL
-- to generate current UTCModDate
SELECT julianday('now') - 2415018.5 AS UTCModDate

-- to convert UTCModDate to standard format UTC date/time
SELECT UTCModDate,
DATE(UTCModDate + 2415018.5) AS Date,
TIME(UTCModDate + 2415018.5) AS Time,
DATETIME(UTCModDate + 2415018.5) AS DateTime
FROM EventTable



-- Update the UTCModDate to the current time stamp:
UPDATE SourceTable
SET UTCModDate = julianday('now') - 2415018.5;

-- Select and convert UTCModDate to standard format UTC
SELECT datetime(UTCModDate + 2415018.5)
FROM SourceTable ;

-- or to local time:
SELECT datetime(UTCModDate + 2415018.5, 'localtime')
FROM SourceTable ;
  
```