How do I increment a java.sql.Timestamp by 14 days?

Question

I have an app that takes a Timestamp as a boundary for the start date and end date of a sql selection, I want to populate a hashmap with weeks this year since the first mon

Answer 1

It worth noting that 14 days is not always 14 * 24 * 3600 seconds. When you have daylight savings, this can be an hour shorter or longer. Historically it can be much more complex than that.

Instead I would suggest using JodaTime or the Calendar to perform the time zone dependant calculation.

Answer 2

private Long dayToMiliseconds(int days){
    Long result = Long.valueOf(days * 24 * 60 * 60 * 1000);
    return result;
}

public Timestamp addDays(int days, Timestamp t1) throws Exception{
    if(days < 0){
        throw new Exception("Day in wrong format.");
    }
    Long miliseconds = dayToMiliseconds(days);
    return new Timestamp(t1.getTime() + miliseconds);
}

Answer 3

java.sql.Timestamp ts = ...
Calendar cal = Calendar.getInstance();
cal.setTime(ts);
cal.add(Calendar.DAY_OF_WEEK, 14);
ts.setTime(cal.getTime().getTime()); // or
ts = new Timestamp(cal.getTime().getTime());

This will correctly cater for daylight-time transitions in your default Timezone. You can tell the Calendar class to use a different Timezone if need be.

Answer 4

Java 8

Timestamp old;
ZonedDateTime zonedDateTime = old.toInstant().atZone(ZoneId.of("UTC"));
Timestamp new = Timestamp.from(zonedDateTime.plus(14, ChronoUnit.DAYS).toInstant());