Search for files after a relative date using Windows search

For the first part of your question: R00UUUUUUUUZZXD-30NU tells Windows to search the last 30 days. Changing 30 to 1 (i.e., R00UUUUUUUUZZXD-1NU) would make it search the last 24 hours.

In your case you are looking to set the value to R00UUUUUUUUZZXD-7NU. Reference this forum post.

For the second part of your question perhaps start by looking at the System.DateModified documentation. The other type that's mentioned, System.StructuredQueryType.DateTime, I am unable to find documentation on.

Update:

I found this gem that gets us closer to deciphering how to construct the relative DateTime values. Consider this quote:

For example, Structured Query supports relative date/time expressions, which remain unresolved until they are applied to some reference time. In a leaf node with semantic type System.StructuredQueryType.DateTime, the value can be either a VT_FILETIME or a VT_LPWSTR. VT_FILETIME is an absolute date/time so it is already resolved. VT_LPWSTR is a string representation of a relative date/time expression. The specified reference time should be a local time, but the resolved times in the resulting query expression will be in coordinated universal time (UTC).

and finally this forum posting has another example of what the DateTime is stored.

The best I can tell it is a relative date/time format. I am still unable to find any hard documentation on it.