Named wrappers over the instant / local-date-time dance

The multiplatform date-time library deliberately separates an instant (a point on the timeline) from a local date-time (wall-clock fields with no zone attached), and converting between them needs a zone every time. Written inline, that is three lines of ceremony around one intent, so the kit is worth having:

// adapted
private val zone get() = TimeZone.currentSystemDefault()

fun now(): LocalDateTime = Clock.System.now().toLocalDateTime(zone)

fun epochMillisToLocalDateTime(epochMillis: Long): LocalDateTime =
    Instant.fromEpochMilliseconds(epochMillis).toLocalDateTime(zone)

fun LocalDateTime.plusSeconds(seconds: Long): LocalDateTime =
    this.toInstant(zone).plus(seconds, DateTimeUnit.SECOND, zone).toLocalDateTime(zone)