Herbert was the middle son of Reverend Benjamin William Day, who was the Rector of St Peter’s Church, Sandwich, in Kent, and his wife Mary Sophia. He was born at the home of his maternal grandmother in Leinster Square, Paddington, on the 14th November 1881.
In September 1894, both Herbert and his elder brother Harold were admitted to the school — Herbert as an exhibitioner – and joined Ashburnham. Herbert was made a monitor in 1899, and received his house colours in the same year. He represented Ashburnham in the winning football team in 1900 and also won the Fives Ties, along with Parker, “after a series of excellent games”.
In 1900, Herbert was elected to an exhibition at Christ Church, Oxford, with a Triplett scholarship. He earned his BA in 1905, and then went on to a career in “the scholastic profession”. He seems to have become a teacher at Wellesley House Prep School, Broadstairs, by 1911.
On the outbreak of war, the three Day brothers — Harold, Herbert and Maurice — joined the army. Herbert enlisted in the The Buffs (East Kent Regiment) and became a Lieutenant with the 11th (Reserve) Battalion Loyal North Lancashire Regiment on the 10th March 1915. The following May, Herbert received the news that his younger brother Maurice, also a former pupil, had died on 9th May 1915 at Aubers Ridge, France.
Herbert was sent out to the western front in June 1916, where he was attached to the 8th Battalion of his regiment. The Loyal North Lancashire Regiment travelled from L├®alvillers to Forceville on the 1st July 1916, and on to Aveluy Wood on the 2nd. They spent some time manning reserve positions at Crucifix Corner before moving to the front line on 7th July.
At La Boiselle on 10th July 1916, the Regiment attacked a German trench. Herbert was killed in the counter-attacks that followed, along with 74 other members of the Lancashire regiment.