Timeline
The first story, A Thousand Kisses, starts just before Christmas.
23 December: The exhibition of Christ. In the first sequence Caesar Gabriel asks his friends, Leopard Solid and Sugar Plum, "By the way, what are you doing for Christmas Eve Tomorrow?"
24 December: Thefts and accusations. Series of thefts from the Metropolian, the Louvre and National Gallery appears to start at midnight between 23 December and 24 December. Broadcasts of the news are, presumably, the same morning, 24 December. The theft of Christ from Lady Devlin appears to have happened later the same night, as the broadcast ends with the dramatic "Who is this 'Eroica' and what can we expect from them", fading out to an image of the Earl's airplane, where someone says "Lady Devlin ought to be up in arms now." Leopard, Sugar and Caesar are then called back to Lady Devlin's house, presumably also on the 24th of December. Afterwards (again, persumably on the same day), they discuss the matter and Sugar foretells that something will happen "10 days from now".
3 January?: the Tate Gallery. 10 days for now would make the Tate Gallery incident on the 3rd of January.
4th of January?: The Archangel Gabriel, making of. Soon after the Tate Gallery, maybe the next day, Sugar Plum and Leopard Solid starts on their project of making a statue of the Archangel Gabriel. They estimate that this will take them a week.
11 January?: The Archangel Gabriel, burial. If their projections of a week to make the statue holds, burial of the Archangel Gabriel statue could takes place roughly on January 11.
12 January-19 January?: The Archangel Gabriel, finding. It is unclear if more time passes between the statue is dug down an the statue is found, as the monk who finds it only mentions a barking dog. The dog could have barked due to the statue being dug down, but could, of course, be due to something else. Caesar does comment, on seeing the statue in the newspapers that "Produce of the late Renaissance? Bah! It was made last week!" So presumably not more than a week had passed.
15 January-22 January?: The Archangel Gabriel, stealing. On seeing the article about the Archangel Gabriel statue, Dorian decides to steal it "in three days time, at midnight".
The second story, Iron Klaus, takes place six months after the first story, so presumably around July. While it is not explicitly stated, it might take place over two days time, as only one night is shown and the other events might take place in the day before and the day after.
Read more about this topic: From Eroica With Love