NY Times Crossword
August 20, 2013
Zhouqin Burnikel and Dan Gagliardo

What do the following word and phrases have in common?

FIELDWORK
HOLY WEEK
LABOR MARKET
LUCKY DOG

HINT:
Supposed inventor of baseball

Answer:

Each half of the compound word and both words in the phrases can be followed by DAY:

Field day, Work day, Holy day, Weekday, etc. 

(HINT: Abner DOUBLEDAY)