add standard time block if only daylight time block

Currently, if all events are in daylight time for a particular team, ri_cal will only build the Daylight time block.  Unfortunately, Yahoo! doesn't do well with that.  They can't seem to figure out what the actual time of the game is.  As soon as a game is added in Standard time, the Standard time block is created and Yahoo! starts figuring out event times.  Let's always add the Standard time block if we only have the Daylight period.