Convert time (without date) to UTC time in Scala - scala

Question

I have a string of time I need to parse that's currently in a 12 hour clock format. Some examples are the following:
11:30 PM
07:00 AM
These times are currently in eastern time zone. What's the best way to convert those strings to a string that contains the UTC equivalent?

Answer 1

How about:
import java.text.SimpleDateFormat
val fmtFromLocal = new SimpleDateFormat("hh:mm a z") // z parses time zone
val fmtToGmt = new SimpleDateFormat("hh:mm a")
def toGmt(t: String): String = fmtToGmt.format(fmtFromLocal.parse(s + " EST"))
Unfortunately, this fails when the local timezone is not GMT, as .parse() returns a local time.
Corrected:
import java.text.SimpleDateFormat
import java.util.{Date, TimeZone}
val localTz = TimeZone.getDefault()
val currentOffset = localTz.getOffset(System.currentTimeMillis)
val fmtFromLocal = new SimpleDateFormat("hh:mm a z") // z parses time zone
val fmtToGmt = new SimpleDateFormat("hh:mm a")
def toGmt(t: String): String = {
val time = fmtFromLocal.parse(t).getTime()
val timeUtc = time + currentOffset
fmtToGmt.format(new Date(timeUtc))
}
(Not tested)

Answer 2

Use Joda-Time.
val tz = DateTimeZone.forTimeZone(TimeZone.getTimeZone("EST"))
// You can also use DateTimeZone.forID(), but it requires an id in form
// like 'Europe/Paris', but I don't remember which such ID corresponds to Eastern time
val fmt = DateTimeFormat.forPattern("hh:mm a")
val fmtIn = fmt.withZone(tz)
val fmtOut = fmt.withZone(DateTimeZone.UTC)
val strIn = "11:30 PM"
val strOut = fmtOut.print(fmtIn.parseDateTime(strIn))
Easy and pretty straightforward. I'm getting 04:40 AM for 11:30 PM, which seems to be correct, and I'm in UTC+4 zone, so it this method works independently on local time zone.