Finding points in one layer within range of time of points in another layer using QGIS

I am very new to QGIS and SQL.

I have two layers, each is populated with points and temporal data. One layer has information on battles occuring in Iraq and Syria, and the other has information on terror attacks. I would like to extract information about the distance of each terror attack to the nearest battle, within 30 days.

I have two SpatiaLite layers and have tried the following query to create a new virtual layer:

SELECT battles.data_id as id_battles, terror.fid as id_terror,
       ROUND(MIN(ST_Distance(acled.geometry, fullset.geometry)),2) AS distance
FROM ACLED AS battles, FullSet_Prio2 AS terror
WHERE battles.'date' BETWEEN terror.'date' AND (terror.'date' - 1 month)
GROUP BY terror.fid
ORDER BY distance DESC

This returns a syntax error at the -1 month line. +

The query works if I use == instead of WHERE...BETWEEN...AND but that’s not the information I need.

Could anyone help me figure out the correct syntax for substracting from dates or do I need to do something else instead?

I tried creating a virtual layer using this:

WHERE day(age(fullset.'date', acled.'date')) < 30

This doesn’t result in an error, but results in empty rows.