Modern Java date-time APIs separate date, local date-time, instant, offset, and time zone.

Instant now = Instant.now();
LocalDate today = LocalDate.now();
ZonedDateTime india =
    ZonedDateTime.now(ZoneId.of("Asia/Kolkata"));

Duration duration = Duration.between(
    now, now.plusSeconds(30)
);

Use Instant for machine-oriented points in time, LocalDate for a date without a zone, and ZonedDateTime when location matters.

For financial systems, BigDecimal is generally preferred when decimal arithmetic must be exact.