When should you buy a used car? iSeeCars.com took a look at 40 million used car sales from 2013 to 2015 and figured out the best times to find top deals — and when buyers have to do more work to find the right price.

According to the site, the days with the most deals offered are usually late in the year around the holidays, with up to 33 percent more deals found than on an average day. However, some holidays throughout the year beat out the traditional best time for buying a car during end-of-year closeouts in November and December.

As the weather warms up, used-car deals become harder to find, with the iSeeCars.com report finding that the spring and summer months had up to 28 percent fewer deals during these times than on an average day.

Check below to see the results from iSeeCars.com and find out the best and worst days for deals.

10 best times to find a used-car deal

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Here are the best times to find a deal on used cars:

10. New Year's Eve

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The final days of the year are the 10th-best time of year to buy a car, according to data from iSeeCars.com, which found that 21.3 percent of used-car sales deals are better than average around Dec. 31.

9. Christmas

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As the end of the year draws near, Christmastime is the ninth-best time to buy a used car, according to iSeeCars.com, with 21.4 percent more deals than average.

8. Month of December

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The last month of the year was the eighth-best time to buy a used car, with 23.5 percent more deals than average.

7. Month of November

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November is the seventh-best time to buy a used car, with 26.9 percent of the deals below average during that month.

6. Christmas Eve

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Last-minute car shopping on Christmas Eve isn't a bad thing, as 28.7 percent of used-car sales are deals on that day, according to iSeeCars.com.

5. Martin Luther King Jr. Day

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The only ideal time in the first nine months of the year to purchase a vehicle is Martin Luther King Jr. Day, Jan. 20, when 29.4 percent of used cars have better than average deals.

4. Columbus Day

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With fall's arrival, the peak in used-car deals begins around Columbus Day, with 30.5 percent more deals that are below average, according to iSeeCars.com.

3. Thanksgiving

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Turkey, football and ... car buying? Thanksgiving is the third-best day to buy a car, with 30.6 percent more deals than the average day.

2. Veterans Day

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The second-best day of the year to buy a car is Veteran's Day (Nov. 11). iSeeCars.com found that 32.5 percent more deals were offered on that day.

1. Black Friday

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Black Friday isn't only one of the best days of the year for shopping, but is also the best day of year to buy a used car, according to iSeeCars.com. Used-car deals on the day after Thanksgiving are 33.1 percent better than average on that day, according to the site.

10 worst times to find a used car deal

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Here are the toughest times to find a deal on used cars:

10. Month of July

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July has fewer deals than most times of the year, according to iSeeCars.com, as 11.5% of deals during the month are below average.

9. Father's Day

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Father's Day is a good time to work on cars, but not the best to buy used ones. Per iSeeCars.com, it's the ninth-worst day to find a used car deal, with 18.3% of deals below an average day.

8. Memorial Day

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Memorial Day is a day for honoring those who made the ultimate sacrifice for their country while serving in the armed forces. It isn't, however, for buying used cars, according to iSeeCars.com, with 18.3 percent fewer deals than an average day, according to iSeeCars.com.

7. Good Friday

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Good Friday isn't necessarily a good time to buy a used car, with 21.6% less deals found on that day than a typical one.

6. Easter

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While they aren't eggs, Easter will have you hunting harder for a used car deal than most other days of the year, with 22.2% less deals than an average day.

5. Month of June

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According to iSeeCars.com, June is the fifth-worst time of year to buy a car, with 23.6% of the deals being below those on an average day.

4. Month of May

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May is the fourth-worst time of year to buy a used car, according to iSeeCars.com, with 26.0% less deals to be found in the fifth month of the year.

3. Month of April

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Tax season isn't necessarily used-car-buying season, with iSeeCars.com finding 27.0% less deals in the month than an average day.

2. Mother's Day

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While moms are the best, Mother's Day isn't for buying used cars -- there are 27.5 percent fewer deals that day, according to iSeeCars.com.

1. July 4

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Independence Day is the worst day for deals on used cars, with 28 percent fewer deals found on July 4 than on an average day, according to iSeeCars.com.

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