The different use of the word “day” in the Quran is a miraculous phenomenon. While the singular word “a day” is used 365 times, the plural of it (eyyam, yewmeyn) is used 30 times. This represents the number of the days in a month which is 30. So it is meaningful that while the singular “day” (yewm) is mentioned 365 times, the plural of it (eyyam, yevmeyn) is mentioned 30 times.
In the solar calendar, the months have either 30 or 31 days and in the lunar calendar the months have either 29 or 30 days. So, the number 30 is the intersection group for both calendars. In the community to which the Quran was revealed, the lunar calendar was in use; the mention of “30” is therefore meaningful. It takes 29.53 days for the moon, the planet in the sky, to make a month. The rounded figure is 30. With such mathematical miracles, we witness that the Quran calculates correctly this rounding up bussiness. Likewise, the world completes its cycle around the sun in 365.25 days exactly. The rounded figure is 365.