How can I convert a date in YYYYMMDDHHMMSS format to epoch or unix time?

Question

EDIT: I have edited my question to include more information, I have tried many ways to do this already, asking a question on StackOverflow is usually my last resort. Any hel

Answer 1

tl;dr

LocalDateTime
.parse(
    "20140430193247" , 
    DateTimeFormatter.ofPattern( "uuuuMMddHHmmss" )
)
.atOffset(
    ZoneOffset.UTC
)
.toEpochSecond()

java.time

Parse your input string as a LocalDateTime as it lacks an indicator of offset-from-UTC or time zone.

String input = "20140430193247" ;
DateTimeFormatter f = DateTimeFormatter.ofPattern( "uuuuMMddHHmmss" ) ;
LocalDateTime ldt = LocalDateTime.parse( input , f ) ;

Now we have a date with time-of-day, around half-past 7 PM on April 30 of 2014. But we lack the context of offset/zone. So we do not know if this was 7 PM in Tokyo Japan or 7 PM in Toledo Ohio US, two different moments that happened several hours apart.

To determine a moment, you must know the intended offset/zone.

If you know for certain that an offset of zero, or UTC itself, was intended, apply the constant ZoneOffset.UTC to get an OffsetDateTime.

OffsetDateTime odt = ldt.atOffset( ZoneOffset.UTC ) ;

How can I convert this into Epoch/Unix time?

Do you mean a count of seconds or milliseconds since the first moment of 1970 in UTC?

For a count of whole seconds since 1970-01-01T00:00Z, interrogate the OffsetDateTime object.

long secondsSinceEpoch = odt.toEpochSecond() ;

For milliseconds, extract a Instant object. An Instant represents a moment in UTC, and is the basic building-block class of java.time. Then interrogate for the count.

Instant instant = odt.toInstant() ; 
long millisSinceEpoch = instant.toEpochMilli() ;

Answer 2

I got the answer after quite a while of trying different ways. The solution was pretty simple - to parse the time to a string as toString() didn't work.

    Date date;
    SimpleDateFormat df = new SimpleDateFormat("yyyyMMddHHmmss");

    try {
        date = df.parse(String.valueOf(_time.getTime()));
    } catch (ParseException e) {
        throw new RuntimeException("Failed to parse date: ", e);
    }

    return date.getTime();