The phrase "and certain days of" is correct and usable in written English.
It can be used when referring to specific days within a broader context, such as a schedule or a timeframe.
Example: "The event will take place on weekends and certain days of the week."
Alternatives: "and specific days of" or "and particular days of".
"Calendar effects" were the most striking: at certain times of the year and on certain days of the week, prices predictably rise (or fall) by more (or less) than on the average day, and the related returns vary correspondingly.One example is the "January effect": shares of small companies beat the market in January.
Religious leaders proclaimed the Peace of God and the Truce of God, designed to halt or at least limit warfare and assaults during certain days of the week and times of the year and to protect the lives of clergy, travelers, women, and cattle and others unable to defend themselves against brigandage.
The Times began printing stand-alone sections for sports and metropolitan news on certain days of the week in the 1970s and '80s; in the '90s, each became a separate section every day of the week.
The special meal, with wine pairings, can be for up to four guests and is only available certain days of the week.
The efforts to limit water irrigation to specific hours of the day, during certain days of the week seem prudent.
"He's walking back and forth to work on certain days of the week, except when it's raining," she said.
Most of the deals are valid for flights from Aug. 23 through Dec. 14, and they're limited to certain days of the week.
Two nurses and a general practitioner serve patients here daily, while a paediatrician and dermatologist are available on certain days of the week.
Note: there are certain days of the year (April Fool's Day, Closing Day) where detecting Apparti Antiquus are difficult due to large numbers of imitators infiltrating the mountain.
