int <- new_interval(ymd("2001-01-01"), ymd("2002-01-01"))
# 2001-01-01 UTC--2002-01-01 UTC
int_start(int)
# "2001-01-01 UTC"
int_start(int) <- ymd("2001-06-01")
int
# 2001-06-01 UTC--2002-01-01 UTC
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