Before this change isToday() would stop working in Y2038
because android.text.format.Time doesn't work after Y2038.
This commit fixes the code by using java.time classes that
are Y2038 safe.
Bug: 16550209
Test: atest android.text.format.cts.DateUtilsTest
Change-Id: Ied339a694819c308add8645c7434b645dc1ccdde