New supported format: . [rt #67780 - Colm Dougan] Conditionally rewrite date strings, currently ones with an 'at' followed by a time or daytime (e.g., noon). Place the rewrite data in the grammar class; add an accessor. Adapt the grammar by merging or removing now superfluous entries. Mention rewriting by use of a comment in the grammar class. Rewrite all patterns and refine handling punctuation marks when extracting parsable expressions; add tests. Make generation of time entries for tests capable of processing the {at} placeholder and use it within the test strings. Test parsing of date strings with rewritten time precision.