Since the season of Jewish High Holidays Rosh Hashanah (the New Year) and Yom Kippur (Day of Atonement) follows the lunar calendar, it's not always straightforward to predict when they'll fall. Jewish holidays begin at sunset.
To keep track, download a Jewish calendar for your smartphone. Available in Hebrew and English, they can be as elaborate as naming the Torah portion for each Friday night Shabbat service or as simple as letting you know when the major holidays occur. Check out a sample at here
You can also set your Outlook to identify Jewish holidays and when you sync with your handheld, those holidays will appear on your mobile.
1. Open you calendar in Outlook
2. Select Tools --> Options, and click on Calendar Options.
3. Click the Add Holidays button.
4. Select the countries or religions (in this case Jewish) whose
holidays you want to add and click OK.
Sync your PC with your Windows Mobile, iPhone, Palm OS device -- whatever (as long as it's compatible with Outlook) -- to transfer the holidays onto your smartphone.