Diego Lopez had Valencia ahead, before Celta struck via Oscar Mingueza, Iago Aspas and Fran Beltran.
Giraldez beamed afterwards: "It's an anecdote but all Celta fans deserve to live days like these. I think it has been a very nice day for the result, for the game, for the atmosphere and for the synergies between fans and players, which are greater every day.
"And also for the anniversary date. Very happy because it is one more way to build Celticism and the classification is anecdotal at this point. We are already thinking about Villarreal."
On veteran Aspas, Giraldez also said: "Every day I see him better, he is going to retire us all. Very happy with the contribution he is having, with the physical level he is showing, we are seeing him very well.
"It is a pleasure to see how that head works, with the enthusiasm he shows daily."