The date is only accurate to the month.
Found on a foray sponsored by the Los Angeles Mycological Society. Identification by sight and smell corroborated by Paul Harding.
All I found surfing the web was the following key:
3. Edge of the cap fairly bright yellow at maturity.
3. Edge of the cap not bright yellow at maturity.
I wouldn’t not call the margin of the cap ‘fairly bright yellow’, but these were certainly not mature so I’m still a bit torn. I also remember that these were unusally small based on my experience in northern California. The caps were about an inch across. I’m going up to the San Bernardinos in a few weeks so I’ll keep an eye out for more specimens.
Using Smith, Smith & Weber this photo seems to key to Floccularia pitkinensis by default. “How to know the Gilled Mushrooms” states the margin is ivory yellow [30A2] and the disc is avellaneous [7B3] which are good matches in Methuen Handbook of Colour.