When an insured period is calculated, this is done in months; the months from that in which a person acquires the status of an insured to the month preceding that in which the person forfeits that status are used to calculate it.
被保険者期間を計算する場合には、月によるものとし、被保険者の資格を取得した月からその資格を喪失した月の前月までをこれに算入する。
If, in the same month that a person has acquired the status of an insured, the person forfeits that status, that month is calculated as a one-month long insured period; provided, however, that this does not apply if the person acquires the status of an insured or an insured under a National Pension (excluding a category II insured specified in Article 7, paragraph (1) item (ii) of the National Pension Act) again in that month.
被保険者の資格を取得した月にその資格を喪失したときは、その月を一箇月として被保険者期間に算入する。ただし、その月に更に被保険者又は国民年金の被保険者（国民年金法第七条第一項第二号に規定する第二号被保険者を除く。）の資格を取得したときは、この限りでない。
For a person who has acquired the status of an insured again after having forfeited that status, the previous and subsequent insured periods are added up.
被保険者の資格を喪失した後、更にその資格を取得した者については、前後の被保険者期間を合算する。
The provisions of the preceding three paragraphs apply for each insured category.
Notwithstanding the provisions of paragraph (2) that were to have been applied pursuant to the provisions of the preceding paragraph, if a person has undergone a change of insured categories in the same month, that month is deemed to be a month in which the insured was under the insured category from after the change (if the insured has undergone a change of insured categories twice or more in the same month, that month is deemed to be a month in which the insured was under the last of those insured categories).
Read this with the articles around it
When an insured period is calculated, this is done in months; the months from that in which a person acquires the status of an insured to the month preceding that in which the person forfeits that…
被保険者期間を計算する場合には、月によるものとし、被保険者の資格を取得した月からその資格を喪失した月の前月までをこれに算入する。
Open this provisionIf, in the same month that a person has acquired the status of an insured, the person forfeits that status, that month is calculated as a one-month long insured period; provided, however…
被保険者の資格を取得した月にその資格を喪失したときは、その月を一箇月として被保険者期間に算入する。ただし、その月に更に被保険者又は国民年金の被保険者（国民年金法第七条第一項第二号に規定する第二号被保険者を除く。）の資格を取得したときは、この限りでない。
Open this provisionFor a person who has acquired the status of an insured again after having forfeited that status, the previous and subsequent insured periods are added up.
被保険者の資格を喪失した後、更にその資格を取得した者については、前後の被保険者期間を合算する。
Open this provisionThe provisions of the preceding three paragraphs apply for each insured category.
前三項の規定は、被保険者の種別ごとに適用する。
Open this provisionStatus as an Insured Person
An insured person of Employees' Pension Insurance (hereinafter referred to as a "category 2 insured person");
厚生年金保険の被保険者（以下「第二号被保険者」という。）
Open this provisioninsured category
「被保険者の種別」
Which of the four categories of insured under Employees' Pension Insurance (厚生年金保険) a person falls in: category I (第一号厚生年金被保険者), category II (第二号厚生年金被保険者), category III (第三号厚生年金被保険者) or category IV (第四号厚生年金被保険者) (Article 15).
Defined inArticle 15, paragraph (1)