java.text.ParseException: Unparseable date: "09:07:31 AM PDT"

I have a field in the response that is coming as time which I want to parse before adding some minutes into it. I have written the below code which results in error.

SimpleDateFormat df = new SimpleDateFormat("HH:MM:ss a SSS");
        Date date = df.parse(currentTime);
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        cal.add(Calendar.MINUTE, 10);

here, currentTime is coming in as "09:07:31 AM PDT"

tl;dr

LocalTime                                        // Represent a time-of-day without a date and without a time zone or offset-from-UTC.
.parse(               
"09:07:31 AM PDT".substring( 0 , 11 ) ,      // Remove the senseless `PDT` from the input.
DateTimeFormatter.ofPattern( "hh:mm:ss a" )  // Define a formatting pattern to match our modified input string.
)                                                // Returns a `LocalTime` object.
.toString()                                      // Generates text in standard ISO 8601 format to represent the value of our `LocalTime` object.

>09:07:31

Avoid Date & Calendar

You are using terrible date-time classes that were bundled with the earliest versions of Java. These were supplanted years ago by the modern java.time classes defined in JSR 310.

Never use Date, Calendar, SimpleDateFormat, and such.

Date class does not fit

The java.util.Date class represents a moment, a date with time-of-day, as seen in UTC. Your input lacks a date. So your input cannot be represented by this class.

Time-of-day with zone makes no sense

Your input represents a time-of-day with what is a false time zone. The PDT likely stands for "Pacific Daylight Saving Time", to indicate whether Daylight Saving Time (DST) is in effect or not. This is not a true time zone name. Instead a time zone name such as America/Los_Angeles should be used.

At any rate, the combination of a time-of-day with a time zone makes no sense. Without the context of a date, the time zone carries no meaning.

LocalTime

I suggest you extract the time-of-day and ignore the PDT. Take the first 11 characters.

String input = "09:07:31 AM PDT";
String s = input.substring( 0 , 11 ); // Uses annoying zero-based index counting. So asking for first through the eleventh characters requires ( 0 , 11 ).

Define a formatting pattern to match our modified input string.

DateTimeFormatter f = DateTimeFormatter.ofPattern( "hh:mm:ss a" );

Parse as a LocalTime, a time-of-day without a date and without a time zone or offset-from-UTC.

LocalTime lt = LocalTime.parse( s , f );

>lt.toString(): 09:07:31

ZonedDateTime

For fun, let's apply a time zone to your time-of-day, and a date to get a ZonedDateTime.

LocalTime lt = LocalTime.parse( "01:59:00 AM PDT".substring( 0 , 11 ) , DateTimeFormatter.ofPattern( "hh:mm:ss a" ) );
LocalDate ld = LocalDate.of( 2020 , Month.MARCH , 7 );
ZoneId z = ZoneId.of( "America/Los_Angeles" );
ZonedDateTime zdt = ZonedDateTime.of( ld , lt , z );
ZonedDateTime zdtLater = zdt.plusMinutes( 5 );
System.out.println( "zdtLater = " + zdtLater );

We get 2:04 AM.

>zdtLater = 2020-03-07T02:04-08:00[America/Los_Angeles]

Change that date to the 8th.

LocalTime lt = LocalTime.parse( "01:59:00 AM PDT".substring( 0 , 11 ) , DateTimeFormatter.ofPattern( "hh:mm:ss a" ) );
LocalDate ld = LocalDate.of( 2020 , Month.MARCH , 8 );
ZoneId z = ZoneId.of( "America/Los_Angeles" );
ZonedDateTime zdt = ZonedDateTime.of( ld , lt , z );
ZonedDateTime zdtLater = zdt.plusMinutes( 5 );
System.out.println( "zdtLater = " + zdtLater );

We get 3:04 AM, not 2:04 AM.

>zdtLater = 2020-03-08T03:04-07:00[America/Los_Angeles]

The date is what gives meaning to that time-of-day in a time zone.

Offsets vary over time. That is the meaning of a time zone. A time zone such as America/Los_Angeles is a history of the past, present, and future changes to the offset used by the people in many regions on the west coast of North America. On March 7, 2020 the offset was eight hours behind UTC. On March 8, 2020, the offset was changed to seven hours behind UTC. At the first moment of 2 AM, the clock jumped an hour to 3 AM. The 2 AM hour never happened on the 8th as it did on the 7th.

OffsetTime

The java.time framework does offer the OffsetTime class. This represents a time-of-day with an offset-from-UTC.

This class makes no sense, for the same reasons discussed above. A time-of-day with an offset but no date serves no useful purpose. I presume this was added to java.time merely to match the SQL-standard type TIME WITH TIME ZONE, in parallel with LocalTime matching TIME WITHOUT TIME ZONE. But this TIME WITH TIME ZONE type makes no sense in SQL. This problem is noted by others, not merely my opinion. And this is not the only senseless thing in the SQL standard.

Furthermore, your input carries a time zone (or at least a time zone was intended by the mis-use of PDT), not an offset. An offset is a number of hour-minutes-seconds, nothing more. A time zone is a history of changes in offset, as discussed above.

You need to use the right combination of letters in format, here:

SimpleDateFormat df = new SimpleDateFormat("HH:mm:ss aa zzz");

You might also want to look at API docs 1.

Note: Parsing would work if you use the above format, but you will need the date part as well for accurate calculations. Here is an example with the current date of the current timezone of your machine used as the date part.

        String recievedTime = "09:07:31 AM PDT";
        String currentDate = new SimpleDateFormat("yyyy-MM-dd").format(new Date());
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss aa zzz");
        Date date = df.parse(currentDate +" " + recievedTime);

1 https://docs.oracle.com/javase/8/docs/api/java/text/SimpleDateFormat.html