Reading: 日々【ひび】 or 日々【にちにち】?

Question

There is an explanation of the difference between 日々 vs 毎日 here:

https://japanese.stackexchange.com/a/42641/31150

but it does not mention the reading of 日々, which wwwjdic says can be 日々【ひび】 or 日々【にちにち】

In some related entries, wwwjdic lists the expressions

一日一善 【いちにちいちぜん】 doing a good deed each day

一日一日 【いちにちいちにち】 gradually; day by day

一日一歩 【いちにちいっぽ】 one step each day

Then there are two sentences in an article from today's Asahi using both 一日 and 日々,

一日【いちにち】一首【いっしゅ】

A poem a day.

日々【ひび】感【かん】じた思【おも】いのすべてを歌【うた】にする。

I write a poem about everything I feel every day.

https://www.asahi.com/articles/ASR1W4SJ1R1NULUC001.html?iref=comtop_Culture_04

My question therefore is: Are the furigana correct in the two sentences from the Asahi article?

Is it 一日【いちにち】 in the first sentence

and

日々【ひび】 in the second?

PS Adding to the confusion, there also seem to be multiple readings for this expression:

日々是好日; 日日是好日; 日々これ好日 【にちにちこれこうじつ; にちにちこれこうにち; ひびこれこうじつ; ひびこれこうにち】 (exp) (proverb) every day is a good day; enjoy every day

Answer 1

When 日々 means "day by day", "day-to-day" or "everyday" in modern Japanese, you can safely assume its reading is ひび. The にちにち reading is almost obsolete now, and you can find this reading only in a few proper nouns and set phrases including 宮崎日日新聞 and 日日是好日.

日日 can be read ひにち as well, but it's usually written as 日にち to avoid confusion.

一日 is read いちにち when it means "one day" and ついたち when it refers to the first day of the month.