Artikel 15

1. In the cases referred to in Article 10, Article 19, Article 28, paragraphs 1 to 4, Article 49, and Article 51, paragraphs 1 to 3, of the Convention, without prejudice to the provisions of Article 28, paragraph 4, or Article 51, paragraph 3, of the Convention, as the case may be, periods of insurance and periods of residence shall be added together in accordance with the following rules:
(a) to the periods of insurance or residence completed under the legislation of one Contracting Party shall be added the periods of insurance completed under the legislation of any other Contracting Party and also any periods of residence completed after the age of sixteen under the non-contributory scheme of any other Contracting Party, to the extent necessary to make up the total period of insurance or residence required under the legislation of the first Contracting Party for the acquisition, maintenance or recovery of entitlement to benefit provided always these periods do not overlap. In the case of invalidity, old age, or death (pensions) benefits to be paid by the institutions of two or more Contracting Parties in accordance with the provisions of Article 29 of the Convention, each of the institutions concerned shall separately add together all the periods of insurance or residence completed by the person concerned under the legislation of all the Contracting Parties to which he has been subject;
(b) where a period of compulsory insurance completed in accordance with the legislation of one Contracting Party coincides with a period of voluntary or optional continued insurance completed under the legislation of another Contracting Party, the first only shall be taken into account, without prejudice to the provisions of the second sentence of Article 16, paragraph 2, of the Convention;
(c) where an actual period of insurance completed under the legislation of one Contracting Party coincides with a period assimilated to an actual period of insurance under the legislation of another Contracting Party, the first only shall be taken into account;
(d) any period assimilated to an actual period of insurance under the legislation of two or more Contracting Parties shall be taken into account only by the institution of that Contracting Party to whose legislation the person insured was last compulsorily subject prior to the said period; where the insured person has not been compulsorily subject to the legislation of one of those Parties prior to the said period, that period shall be taken into account by the institution of that Contracting Party to whose legislation he was first compulsorily subject after the period in question;
(e) where the time at which certain periods of insurance were completed under the legislation of a Contracting Party cannot be accurately determined, such periods shall be presumed not to overlap with periods completed under the legislation of another Contracting Party and shall be taken into account as may be necessary;
(f) where, according to the legislation of one Contracting Party, certain periods of insurance are taken into account only if they have been completed within a specified time, the institution which applies this legislation shall take into account only periods completed under the legislation of another Contracting Party as have been completed within the same specified time.
2. Periods of insurance completed under a scheme of a Contracting Party to which the Convention does not apply, but which are taken into account by a scheme of that Party to which the Convention does apply, shall be considered as insurance periods to be taken into account for the purpose of adding together.
3. Where the periods of insurance completed under the legislation of one Contracting Party are expressed in units other than those used in the legislation of another Contracting Party, the conversion necessary for the purpose of adding them together shall be governed by the following rules:
(a) where the person concerned has been working a six-day week: (i) one day shall be equivalent to eight hours, and vice versa;
(ii) six days shall be equivalent to one week, and vice versa;
(iii) twenty-six days shall be equivalent to one month, and vice versa;
(iv) three months, or thirteen weeks, or seventy-eight days shall be equivalent to one quarter and vice versa;
(v) for the conversion of weeks into months, and vice versa, the weeks and months shall be converted into days;
(vi) the application of the rules set out above shall not result in a total, for periods completed during one calendar year, of more than three hundred and twelve days, or fifty-two weeks, or twelve months, or four quarters;
(i) one day shall be equivalent to eight hours, and vice versa;
(ii) six days shall be equivalent to one week, and vice versa;
(iii) twenty-six days shall be equivalent to one month, and vice versa;
(iv) three months, or thirteen weeks, or seventy-eight days shall be equivalent to one quarter and vice versa;
(v) for the conversion of weeks into months, and vice versa, the weeks and months shall be converted into days;
(vi) the application of the rules set out above shall not result in a total, for periods completed during one calendar year, of more than three hundred and twelve days, or fifty-two weeks, or twelve months, or four quarters;
(b) where the person concerned has been working a five-day week: (i) one day shall be equivalent to nine hours, and vice versa;
(ii) five days shall be equivalent to one week, and vice versa;
(iii) twenty-two days shall be equivalent to one month, and vice versa;
(iv) three months, or thirteen weeks, or sixty-six days, shall be equivalent to one quarter, and vice versa;
(v) for the conversion of weeks into months, and vice versa, the weeks and months shall be converted into days;
(vi) the application of the preceding rules shall not result in a total, for periods completed during one calendar year, of more than two hundred and sixty-four days, or fifty-two weeks, or twelve months, or four quarters.
(i) one day shall be equivalent to nine hours, and vice versa;
(ii) five days shall be equivalent to one week, and vice versa;
(iii) twenty-two days shall be equivalent to one month, and vice versa;
(iv) three months, or thirteen weeks, or sixty-six days, shall be equivalent to one quarter, and vice versa;
(v) for the conversion of weeks into months, and vice versa, the weeks and months shall be converted into days;
(vi) the application of the preceding rules shall not result in a total, for periods completed during one calendar year, of more than two hundred and sixty-four days, or fifty-two weeks, or twelve months, or four quarters.
4. Where, in accordance with paragraph 1, sub-paragraph (b), of this Article, periods of voluntary or optional continued insurance in respect of invalidity, old age or death (pensions) completed under the legislation of a Contracting Party are not taken into account when adding periods together, the contributions relating to such periods shall be considered as conferring entitlement to increased benefits under the said legislation. Where such legislation provides to supplementary insurance, the said contributions shall be taken into account for the calculation of the benefits due under such supplementary insurance.