If your company is planning to give customers calendars this month, beware. Don’t let your print shop print your company calendar until you’ve first proofread every single word and number and cross-checked it against an accurate reference calendar.

Believe it or not, calendars can be riddled with errors, which can not only embarrass your company and jeopardize your brand’s credibility but also waste thousands of dollars.

Here are some Fortune 500 calendar mistakes I’ve caught as a corporate proofreader:

• Misspelled words.
• Words with typos.
• Days of the week that correspond with the wrong dates. 
(like Tuesday, Dec. 7, 2016 instead of Wednesday, Dec. 7, 2016.)
• Holidays that correspond with the wrong dates.
• Duplicate dates (Dec. 17 printed twice in one month, for example).
• Missing dates (There’s no Dec. 17, just Dec. 16 and Dec. 18).
• Dates that are out of order.
• Days that incorrectly correspond with moon phases (if your calendar includes moon phases).
• Incorrect copyright dates.

The errors can occur when the print shop that’s hired uses a calendar that already contains typos and misspellings and/or when the print shop uses an outdated calendar, one with last year’s days, dates and holidays.

How to proofread holiday calendars:

• Ask your corporate proofreader (if you have one), an editor or someone with a hawk eye to fact-check and proofread your company calendar. (Have additional people proofread, if possible.)
• Proofread all words for correct spelling.
• Proofread all words for typos.
• Follow the spelling and punctuation rules from the Associated Press Stylebook when you use:
  • “Christmas” (never “Xmas”).
  • “New Year’s Eve” (not “New Years’ Eve” or “New Years Eve”).
  • “New Year’s Day” (not “New Year’s day”).
  • “Hanukkah.”
  • The phrases “happy holidays,” “merry Christmas” and “season’s greetings” (lowercase) in a sentence:
    • “We wish you a merry Christmas.”
    • “Have a happy New Year.”
• Have your proofreader find a reliable, up-to-date reference calendar to use while fact-checking and proofreading days, dates and holidays. (Try timeanddate.com.)
• Use the correct calendar to confirm that:
  • Each month contains the correct number of days. (Example: March has 31 days, not 30. And keep in mind that leap year occurs every four years. The last leap year date was Feb. 29, 2016, so the last day of February in 2017 is Feb. 28.)
  • Every date corresponds with the correct day.
  • The correct dates and correct order of dates appear each month (no missing, out-of-order or duplicate numbers).
  • Holiday and observance dates are accurate.
  • Moon phases (if included) are accurate. (Use timeanddate.com as a reference or check your calendar against the Farmer’s Almanac.)
• Confirm that the copyright date (if included) is correct.

Fact-checking and proofreading your company calendar may sound like a lot of work, but it will save you time and money and protect your brand’s reputation.