It is Michaelmas. The Feats of Michael and All Angels. This is a little of what Wickipedia has to say about it:

Michaelmas(/’mɪkəlməs/; also known as the Feast of Saints Michael, Gabriel, and Raphael, the Feast of the Archangels, or the Feast of Saint Michael and All Angels) is a minor Christian festival observed in some Western calendars on 29 September. In some denominations a reference to a fourth angel, usually Uriel, is also added.

In Christian angelology, the Archangel Michael is the greatest of all the Archangels and is honored for defeating Satan in the war heaven.[4]He is one of the principal angelic warriors, seen as a protector against the dark of night, and the administrator of cosmic intelligence.

This painting by Guido Reni, painted in the 17th Century, which is in a church in Rome, shows Michael the archangel, trampling Satan.

It is a typical, traditional depiction of Michael. References to Michael the    archangel can be found in the Bible, at Revelation 12:7-12:

Today, we have decided to celebrate all the angels. Some people believe we are guarded by many angels. Others have found angels in their own neighbourhood. Some have been visited by angels.

7And war broke out in heaven; Michael and his angels fought against the dragon. The dragon and his angels fought back,8but they were defeated, and there was no longer any place for them in heaven.9The great dragon was thrown down, that ancient serpent, who is called the Devil and Satan, the    deceiver of the whole world—he was thrown down to the earth, and his angels were thrown down with him.

10Then I heard a loud voice in heaven, proclaiming,

“Now have come the salvation and the power
the kingdom of our God
the authority of his Messiah,[
for the accuser of our comrades[
b]been thrown down,
accuses them day and night before our God.
11But they have conquered him by the blood of the Lamb
by the word of their testimony,
for they did not cling to life even in the face of death.
12Rejoice then, you heavens
those who dwell in them!
But woe to the earth and the sea,
the devil has come down to you
with great wrath,
he knows that his time is short!”

Let me tell you my angel story. Many years ago – about 20 – a friend of mine – a man who is a priest – was planning a weekend retreat for men, led by a team of men. The week before the retreat, he expressed to me some concerns for some of the team members. One of them in particular, had many problems – illness and other issues happening in his life. My friend had discovered that a few of the participants in the retreat had some similar issues. He told me he was concerned that they needed to have prayer over the whole weekend, to protect them from these issues erupting into something which would disturb the peace and the purpose of the retreat.

Of course, I said, I would pray for them over the weekend. On the Saturday, as I was praying, I suddenly felt as though an encircling guard of angels were standing around my friend and his companions. I continued to pray for them, and enjoyed the idea of the angels.

When I met up with my friend the next week, he told me that all had been well. It was amazing, he said! On the Saturday, as he had been in the chapel, leading morning prayers, he had suddenly felt warmly embraced by the loving protection of God. It came to his mind that there was a circle of angels around the chapel, protecting them all from harm.

God bless your week!             Jennifer