Today (April 1st 2019) new era name was declared by Suga Chief Cabinet Secretary. Don’t misunderstand that his new era name is used from today (April 1st), but it is used from May 1st. However if you mean a fiscal year, you have to use 令和元年度 or 平成31年度 because a fiscal year stars from April 1st and ends March 31st.
This article tells the reason why 令和 was chosen and the meaning of the name.
The source is “万葉集(Manyoshu)”.

https://www3.nhk.or.jp/news/html/20190401/k10011868731000.html
Manyoshu is the oldest collection of Japanese poems. It was compiled in 7 to 8 century and about 4500 poems are contained in 20 volumes. This is a very important book for Japanese history.
Two Chinese characters used for the new era name are used in the introduction of 5th volume of Manyoshu. 32 Poems contained in the volume say about ume blossoms.
The introduction quoted is “初春の令月にして気淑く風和ぎ,梅は鏡前の粉を披き,蘭は珮後の香を薫らす”.
しょしゅんのれいげつにしてきよくかぜやわらぎ,うめはきょうぜんのこをひらき,らんははいごのこうをかおらす.
The meaning of Reiwa

https://www.youtube.com/watch?v=XXK9oJ6iVew
Abe prime minister said “It is suggested that culture is matured in the society where people live thinking each other beautifully. We hope we can take over the nationality of Japan to the next era and Japanese people can make each flower bloom large (achieve each dream).”