Are Article 2(1) and 2(2)(a) and Article 6(1) of Council Directive 2000/78/EC of 27 November 2000 establishing a general framework for equal treatment in employment and occupation and the principles of legal certainty, maintenance of established rights and effectiveness of EU law to be interpreted as precluding national legislation – such as that at issue in the main proceedings – under which the first adjustment of the retirement pension of the group of civil servants who became entitled to a retirement pension (‘total pension’ under the Pensionsgesetz 1965 (‘the 1965 Law on pensions’)) as from 1 December 2021 at the latest is to be made with effect only from 1 January of the second calendar year following the commencement of entitlement to the retirement pension, whereas the first adjustment of the retirement pension of the group of civil servants who became or will become entitled to a retirement pension (‘total pension’ under the 1965 Law on pensions) as from 1 January 2022 is to be made with effect already from 1 January of the first calendar year following the commencement of entitlement to the retirement pension?