一粒万倍日 (Ichiryū manbai bi) signifies a day where a single good deed or investment can grow into something much larger.

Key Information:

It's considered a highly auspicious day for starting new ventures, purchasing items like wallets, or beginning investments, as these actions are believed to multiply.
However, it's advised to avoid starting new bad habits or ending relationships on this day, as these negative actions may also multiply.

Latest News & Trends (2026):

August 2026 features several 一粒万倍日: August 3rd (which is also a triple auspicious day with 大明日 and 天恩日), 13th, 18th, 25th, and 30th.
These dates are highlighted as ideal for making cosmetic and beauty item purchases.
Other auspicious days like 天赦日 (Tensha-bi) and 大安 (Taian) often coincide with 一粒万倍日, creating super powerful lucky days for events like buying lottery tickets or getting married.
While widely recognized, some sources note that the historical origin of 一粒万倍日 is unclear and it might lack original textual basis.