What's the correct way of using hyphens while wrting time with words (e.g. 7:20)?

Really confused with how hyphens must be used in the following examples:

7:20 - "seven twenty" or "seven-twenty"?

7:25 - "seven twenty-five" or "seven-twenty-five"?

Solution 1:

We use a hyphen to separate the hour from the minutes, as in four-thirty, but not if the expression of minutes requires a hyphen, as in four thirty-five.

Authority: The Gregg Reference Manual by William A. Sabin. 9th Edition. McGraw-Hill: New York. 2001. Used with the consent of Glencoe/McGraw-Hill. p. 124.Authority: The Gregg Reference Manual by William A. Sabin. 9th Edition. McGraw-Hill: New York. 2001. Used with the consent of Glencoe/McGraw-Hill. p. 124.

According to this site