Those pesky 24 minutes
So I've recently stumbled upon this strange behavior and it took me some time to figure it out, so I am sharing ;) We have an excel file with time values inside - hours only, no date. Here is an example with single value: We want to read it in java and do something with it - for example we know the document was created somewhere in Poland, and it has times of teleconference meetings with United Kingdom. So let's say we want to convert the hours to London time and send it to somebody in London. What could be simpler? Let's just use excellent apache.poi library, simplest possible way is as follows: import org.apache.poi.EncryptedDocumentException; import org.apache.poi.openxml4j.exceptions.InvalidFormatException; import org.apache.poi.ss.usermodel.*; import java.io.File; import java.io.IOException; import java.time.Instant; import java.time.ZoneId; import java.time.ZonedDateTime; import java.time.format.DateTimeFormatter; import java.util.Iterator; public c