DateTimeUtils.java

package com.occamlab.te.util;

import java.util.regex.Pattern;
import java.util.regex.Matcher;

import org.joda.time.DateTime;
import org.joda.time.format.DateTimeFormatter;
import org.joda.time.format.ISODateTimeFormat;

/**
 * Provides various utility methods to manipulate temporal values.
 * 
 */
public class DateTimeUtils {

    /**
     * Parses a temporal value and returns the beginning instant. If the
     * provided value is an instant, it is returned in the local (server) time
     * zone.
     * 
     * @param timeStamp
     *            a string representation of a temporal value (year, month,
     *            date, or dateTime values conforming to XML Schema datatypes).
     * 
     * @return a String (ISO-8601 syntax) representing the beginning moment of
     *         the given temporal value.
     */
    public static String getBeginningInstant(String timeStamp) {

        // Ensure the string is in proper ISO form (make adjustments from
        // XML-syntax)
        if (timeStamp.endsWith("Z")) {
            // No 'T' even though it ends with a 'Z', so add one
            if (timeStamp.indexOf("T") == -1) {
                StringBuffer buf = new StringBuffer(timeStamp);
                int lastZ = buf.lastIndexOf("Z");
                buf.insert(lastZ, "T");
                timeStamp = buf.toString();
            }
        }
        Pattern pattern = Pattern.compile(".*[+-]\\d{2}:\\d{2}");
        Matcher matcher = pattern.matcher(timeStamp);
        if (matcher.matches()) {
            // There is a timezone, but no 'T', so add one
            if (timeStamp.indexOf("T") == -1) {
                StringBuffer buf = new StringBuffer(timeStamp);
                int lastColon = buf.lastIndexOf(":");
                buf.insert(lastColon - 3, "T");
                timeStamp = buf.toString();
            }
        }
        DateTimeFormatter formatter = ISODateTimeFormat
                .dateOptionalTimeParser();
        DateTime dateTime = null;
        try {
            dateTime = formatter.parseDateTime(timeStamp);
        } catch (Exception e) {
            System.out.println("DateTimeUtils ERROR: " + e.getMessage());
        }

        return dateTime.toString();
    }
}