Compile-time constant expressions that overflow are a potential source of bugs.

Literals without an explicit L suffix have type int, so the following multiplication expression is evaluated as an integer before being widened to long. The value is greater than Integer.MAX_VALUE, so it wraps around to -1857093632.

static final long NANOS_PER_DAY = 24  * 60 * 60 * 1000 * 1000 * 1000;

The intent was probably for the multiplication expression to be evaluated as a long instead of an int.

static final long NANOS_PER_DAY = 24L * 60 * 60 * 1000 * 1000 * 1000;

If you find yourself doing this kind of time based math, consider using an API that provides a safer, more readable solution. For example, on the sub-second scale, see TimeUnit.convert.