noun
very auspicious day
A day considered extremely lucky in the traditional Japanese calendar, often chosen for weddings, business openings, and other important events.
結婚式は大吉日を選んで決めました。
We chose a very auspicious day for the wedding.
大安 is the most auspicious day in the six-day rokuyō cycle, while 大吉日 is a broader term for any extremely lucky day, not limited to the rokuyō system.
Compound of 大 (dai, 'great') + 吉日 (kichijitsu, 'lucky day'), with the reading だいきちにち likely influenced by the on'yomi of 吉 (kichi) and 日 (nichi).