Reference: combineStructs

combineStructs(str1, str2) returns the structure, the set of its members being the union of the corresponding sets of the structures str1 and str2.

Example:

combineStructs(date(0), time(0))

year: 2010
month: 6
day: 23
weekOfYear: 25
dayOfYear: 174
dayOfWeek: 3
hour: 15
minute: 20
second: 34
millisecond: 774

because

date(0)

year: 2010
month: 6
day: 23
weekOfYear: 25
dayOfYear: 174
dayOfWeek: 3

time(0)

hour: 15
minute: 20
second: 48
millisecond: 615.