tl;dr
ZonedDateTime.of(
LocalDate.now( ZoneId.of( "Pacific/Auckland" ) ) // Determine today’s date for a given region.
.plusDays( 1 ) , // Determine day-after, tomorrow.
LocalTime.parse( // Parse string with AM/PM into `LocalTime` object.
"6:51:35 PM" ,
DateTimeFormatter.ofPattern( "h:m:s a" ).withLocale( Locale.US )
) , // Combine date with time-of-day…
ZoneId.of( "Pacific/Auckland" ) // …and zone…
) // …to produce a `ZonedDateTime`, a point on the timeline.
.toString() // Generate a String in standard ISO 8601 format, wisely extended by appending the name of the time zone in square brackets.
2018-02-02T18:51:35+13:00[Pacific/Auckland]
java.time
Parse that incoming string in 12-hour format into a LocalTime
object.
String input = "6:51:35 PM" ;
DateTimeFormatter f = DateTimeFormatter.ofPattern( "h:m:s a" ).withLocale( Locale.US ) ;
LocalTime lt = LocalTime.parse( input , f ) ;
To set your alarm, you'll need a date combined with this time-of-day along with a time zone to determine an actual moment.
The LocalDate
class represents a date-only value without time-of-day and without time zone.
A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.
If no time zone is specified, the JVM implicitly applies its current default time zone. That default may change at any moment, so your results may vary. Better to specify your desired/expected time zone explicitly as an argument.
Specify a proper time zone name in the format of continent/region
, such as America/Montreal
, Africa/Casablanca
, or Pacific/Auckland
. Never use the 3-4 letter abbreviation such as EST
or IST
as they are not true time zones, not standardized, and not even unique(!).
ZoneId z = ZoneId.of( "America/Montreal" ) ;
LocalDate today = LocalDate.now( z ) ;
If you want to use the JVM’s current default time zone, ask for it and pass as an argument. If omitted, the JVM’s current default is applied implicitly. Better to be explicit.
ZoneId z = ZoneId.systemDefault() ; // Get JVM’s current default time zone.
Determine tomorrow by adding a day.
LocalDate tomorrow = today.plusDays( 1 ) ;
Apply the time-of-day and desired time zone to produce a ZonedDateTime
. If your time-of-day is not valid for that date in that zone because of anomalies such as Daylight Saving Time (DST), the class automatically adjusts. Read the doc to be sure you understand and agree to the behavior of those adjustments.
ZonedDateTime zdt = ZonedDateTime.of( tomorrow , lt , z ) ; // Get a specific moment in time given a particular date, time-of-day, and zone.
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date
, Calendar
, & SimpleDateFormat
.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
Where to obtain the java.time classes?