In H2020 projects (EU projects), the maximum embargo that can be "tolerated" is 6 months (then it has to be on arxiv) [12 months for social sciences]. However,

In H2020 projects (EU projects), the maximum embargo that can be "tolerated" is 6 months (then it has to be on arxiv) [12 months for social sciences]. However, all journals are OK with an arxiv post of the submitted (pre-review) manuscript, and this is what every authors should do.