Since so many Trials require a specific weather day or type and so many players have limited playtime, how about creating a 9th day/weather: Ebon.

Just as with the abyssea chests where Ebon light affects all other lights, Ebon day/weather would incorporate the effects of all other elemental days/weather.

So trials that require kills on fire day or in light weather and so forth could all be done on Ebon day/weather.

Also, since there are currently 8 elemental days, with each day roughly taking up 1 hour RL, each one appears roughly every 8hrs ((57 minutes, 36 seconds Earth Time)) it takes a several days for them to move down the clock, this additional elemental day would thus create a faster rotation of the elements on the RL clock.

Just an idea...