This is from The Book of Sun-Dials by Mrs. Alfred Gatty [aka Margaret Scott Gatty], which you can read online at this University of Pennsylvania website.
Saecula Fugiunt
Saecula sic fugiunt, sic lux, sic umbra, theatrum
Donec stelligerum clauserit una dies.
The vocabulary is keyed to the DCC Latin Vocabulary list. There are two words in this poem that are not on the DCC list:
stelliger, stelligera, stelligerum: star-bearing, starry
theātrum (theātrī, n.): playhouse, theater
claudō claudere clausī clausum: close, shut
diēs diēī m./f.: day
dōnec: until
fugiō fugere fūgī fugitum: flee, escape
lūx lūcis f.: light of day
saeculum -ī n.: generation, age, century
sīc: in this manner, thus; sīc . . . ut: in the same way as
umbra -ae f.: shade, shadow
ūnus -a -um: one
