Not in a month of Sundays.

Something is unlikely to happen.  In the Dictionary of Phrase and Fable Brewer quotes Boldrewood in Robbery under Arms:- “Such another chance might never turn up in a month of Sundays.”

Once in a blue moon
means very rarely.  The Oxford Dictionary of Phrase, Saying and Quotation states ‘“to say that the moon is blue” is recorded in the sixteenth century as a proverbial assertion of something that could not be true.’

Moon

Moon

Many moons ago
means a long time ago, literally many months ago.  The lunar month is being referred to here.

It will all be the same in a hundred years.

Something, which seems upsetting now will not matter a century from now…
…it will be lost in the mists of time.

The passage of time tends to blur memories.  Is this where the mists come in?

A nine days’ wonder
is someone or something which is famous for a short time.  After nine days he, she or it will probably be forgotten…
…we may have to wait and see.

Little and often
is a prescription to take something frequently, but in small amounts.  It could be exercise or sipping a soothing liquid for a cough, cold or sore throat, for example.

Rise to the occasion.

An occasion is a special time.  Special times may require special behaviour.  When someone does something surprisingly well, they are said to have risen to the occasion.

Out of sync
is an abbreviation for out of synchronisation.  Here we have a word derived from Greek via Latin.  “Syn” means alike and “Khronos” means time.  I recently saw this misspelled as “out of sink” and that prompted me to include it here!

He thought all his birthdays had come at once.

Something really nice happened to him – even better than a birthday present!

In your birthday suit…

…when I was getting dressed for the party for my seventh birthday, a retired teacher teased me by asking whether I was going in my birthday suit.  I didn’t know what she was talking about.  It is a euphemism for what you are wearing at birth!

Nowadays everyone “prioritises”, but in my youth they reminded me to put first things first.

I enjoy working on my blog.  I hope it can be considered time well spent.

Time and again, time and time again and over and over again all mean repeatedly.

Once and for all.

This is often used in the context of “This is the last time…”

In the Letter to the Hebrews the writer uses it about the only time.  Chapter 10 puts this in context.  The phrase is used in verse 10 (NIV)  And by that will, we have been made holy through the sacrifice of the body of Jesus Christ once and for all.