Converting Epoch Seconds to DMYHMS
Problem
You need to convert
a number of
seconds since 1970 into a
Date
.
Solution
Just use the Date
constructor.
Discussion
“The Epoch” is the time at the beginning of time as far
as modern operating systems go.
Unix time, and some versions of
MS-Windows time, count off inexorably the seconds since the epoch. On
systems that store this in a 32-bit integer, time is indeed running
out. Let’s say we wanted to find out when the Unix operating
system, whose 32-bit versions use a 32-bit date, will get into
difficulty. We take a 32-bit integer of all ones, and construct a
Date
around it. The Date
constructor needs the number of milliseconds since 1970, so we
multiply by 1,000:
/** When does the UNIX date get into trouble? */ public class Y2038 { public static void main(String[] a) { // This should yield 2038AD, the hour of doom for the // last remaining 32-bit UNIX systems (there will be // millions of 64-bit UNIXes by then). long expiry = 0x7FFFFFFFL * 1000; System.out.println("32-bit UNIX expires on " + Long.toHexString(expiry) + " or " + new java.util.Date(expiry)); // Why doesn't it? // Try going from msec of current time into a Date long now = System.currentTimeMillis( ); System.out.println( "Passing " + Long.toHexString(now) + " --> " + new java.util.Date(now)); } }
Sure enough, the program reports that 32-bit Unixes will expire in the year 2038 (you might think I knew that in advance if you were to judge by the name I gave the class; in fact, my ...
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