This is my answer which I'm submitting:
Watson says "It was a cold morning of the early spring..."
March - April
Holmes refers to "the singular experience of Miss Mary Sutherland..."
Late March / Early April
A Case of Identity took place in June 1889.
March - April of 1890
The Copper Beeches was published in June 1892.
1892 or later
The only case in 1891 was The Final Problem.
Not in 1891
Holmes was missing and presumed dead from May 1891 until April 1894.
Was not 1892
Violet Hunter says, "...two nights later...It was a beautiful moonlight night..."
She arrived in England before April 11 1890
There was no moon in the sky in England from April 11 to April 25, 1890.
She arrived in England before April 11 1890
Watson says, "A fortnight went by...The telegram which we eventually received came late one night..."
Holmes and Watson arrived in England 15 days after Violet Hunter
Holmes and Watson went to Winchester on the day following the telegram's arrival.
Holmes and Watson arrived in Winchester following Violet Hunter visited Baker Street
During her visit to Baker Street, Violet Hunter says, "I shall...start for Winchester tomorrow...."
Holmes and Watson arrived in Winchester 14 days after Violet arrived there
Watson says, "...it was just seven when we reached the Copper Beeches...in the light of the setting sun..."
Holmes and Watson arrived in Winchester April 20, 1890 or later in the year
The sun set before 7 p.m. on April 19 and the days preceding.
Holmes and Watson arrived in Winchester April 20, 1890 or later in the year
On the day Violet Hunter first visited Holmes, Watson says, "...Sherlock Holmes, tossing aside the advertisement sheet of the Daily Telegraph..."
Received daily telegraph
15. The Daily Telegraph was not delivered on Sunday.
Violet didn’t go on Sunday
16. April 6, 1890 was a Sunday.
Violet Hunter did not visit Baker Street on April 6, 1890
17. Watson says, "Holmes had been buried in the morning papers all the way down..."
Didn’t come on a Sunday
18. April 20, 1890 was a Sunday.
Holmes and Watson did not arrive in Winchester on April 20, 1890
