The Gregorian calendar, the solar calendar widely used today; essentially equivalent to the Common Era (Western) calendar with rules for leap years.
日本では現在、グレゴリオ暦を使っている。
Japan currently uses the Gregorian calendar.
グレゴリオ暦で彼の誕生日は何月何日ですか？
What is his birthday in the Gregorian calendar?
旧暦とグレゴリオ暦では日付がずれることがある。
Dates can differ between the old lunar calendar and the Gregorian calendar.