diff --git a/src/main/java/com/kosherjava/zmanim/hebrewcalendar/JewishCalendar.java b/src/main/java/com/kosherjava/zmanim/hebrewcalendar/JewishCalendar.java
index 533013d5..8d8e7c92 100644
--- a/src/main/java/com/kosherjava/zmanim/hebrewcalendar/JewishCalendar.java
+++ b/src/main/java/com/kosherjava/zmanim/hebrewcalendar/JewishCalendar.java
@@ -482,7 +482,7 @@ private int getParshaYearType() {
 	 * 
 	 * @return the current <em>parsha</em>.
 	 */
-	public Parsha getParshah() {
+	public synchronized Parsha getParshah() {
 		if (getDayOfWeek() != Calendar.SATURDAY) {
 			return Parsha.NONE;
 		}
@@ -532,7 +532,7 @@ public Parsha getUpcomingParshah() {
 	 * 		{@link Parsha#SHUVA <em>Shuva</em>}, {@link Parsha#SHIRA <em>Shira</em>}, or {@link Parsha#NONE Parsha.NONE} for a regular
 	 * 		<em>Shabbos</em> (or any weekday).
 	 */
-	public Parsha getSpecialShabbos() {
+	public synchronized Parsha getSpecialShabbos() {
 		if (getDayOfWeek() == Calendar.SATURDAY) {
 			if ((getJewishMonth() == SHEVAT && !isJewishLeapYear()) || (getJewishMonth() == ADAR && isJewishLeapYear())) {
 				if (getJewishDayOfMonth() == 25 || getJewishDayOfMonth() == 27 || getJewishDayOfMonth() == 29) {
@@ -593,7 +593,7 @@ public Parsha getSpecialShabbos() {
 	 * 
 	 * @see HebrewDateFormatter#formatYomTov(JewishCalendar)
 	 */
-	public int getYomTovIndex() {
+	public synchronized int getYomTovIndex() {
 		final int day = getJewishDayOfMonth();
 		final int dayOfWeek = getDayOfWeek();
 
diff --git a/src/main/java/com/kosherjava/zmanim/hebrewcalendar/JewishDate.java b/src/main/java/com/kosherjava/zmanim/hebrewcalendar/JewishDate.java
index 0e8a55dd..d3d0df44 100644
--- a/src/main/java/com/kosherjava/zmanim/hebrewcalendar/JewishDate.java
+++ b/src/main/java/com/kosherjava/zmanim/hebrewcalendar/JewishDate.java
@@ -701,7 +701,7 @@ public int getDaysInJewishMonth() {
      * Computes and sets the Jewish date fields based on the provided absolute (Gregorian) date.
      * @param gregorianAbsDate the Gregorian absolute date.
      */
-    private void setAbsDate(int gregorianAbsDate) {
+    private synchronized void setAbsDate(int gregorianAbsDate) {
         if (gregorianAbsDate <= 0) {
             throw new IllegalArgumentException("Dates in the BC era are not supported");
         }
@@ -952,7 +952,7 @@ public void setJewishDate(int year, int month, int dayOfMonth) {
      *             larger a larger number of <em>chalakim</em> such as 793 (<em>TaShTzaG</em>) break the <em>chalakim</em> into minutes (18
      *             <em>chalakim</em> per minutes, so it would be 44 minutes and 1 <em>chelek</em> in the case of 793 (<em>TaShTzaG</em>).
      */
-    public void setJewishDate(int year, int month, int dayOfMonth, int hours, int minutes, int chalakim) {
+    public synchronized void setJewishDate(int year, int month, int dayOfMonth, int hours, int minutes, int chalakim) {
 
         validateJewishDate(year, month, dayOfMonth, hours, minutes, chalakim);