DateTimeFormatter

The java.time types like LocalDate, LocalDateTime, and ZonedDateTime are great in memory, but every time an order is saved to a database, written to a CSV, rendered on a receipt, or read from a payload, the value crosses a boundary and has to become text. DateTimeFormatter is the type that handles both directions: turning a temporal object into a string a human or machine can read, and parsing a string back into the right temporal type. This lesson covers the predefined ISO formatters, custom patterns, locale-aware rendering, thread-safety, common pitfalls, and the small but useful DateTimeFormatterBuilder.