In American English we use the idiom "only on days that end in 'y'" to playfully dismiss accusations of over-indulgence. The typical joke is:
[wife]: "You spend too much time fishing!"
[husband]: "I only fish on days that end in 'y'!"
The juxtaposition of 'only' with "days that end in 'y'" (which is all of them in English) creates a humorous contrast.
Is there a similar idiom in Spanish?
Yo propondría "un día sí y otro también"
Irony is a very difficult thing to translate. The irony in your example is in the fact that every day ends in 'y', in the English language that is. To create a seamless true natural translation it's necessary to identify a commonality amongst all of the days or another entirely different scenario which has no association with time. Spanish has a lot of Catholicism attached to it so it's very likely that a decent translation could be formed from something in that religious context.
So, what happens every day in a Catholic lifestyle that is taken for granted? And how can you keep the translation of such an event from being stereotypical? Anti-ethical? Offensive?
Sólo pesco en los días que yo coma una tortilla.
I used the subjunctive to make it as if eating one might be unlikely, which is unlikely in itself. Tortillas are a daily thing from my experience.
Sólo me tomo cúando respiro.
The irony is that I breathe all the time.
You really have to pick your poison when it comes to translating irony. There is always that possibility of actually saying something that is indeed offensive, or embarrassing, or outright stupid.
En argentina (desconozco otros lugares) se usa
"...de lunes a lunes"
It's not funny/ironic per se and I don't know if it can solve your problem but if you want to even approach to be funny you have to be way shorter than the other examples. The dialogue would be
A- Pescas todos los días
B- No...sólo de lunes a lunes.
Algo parecido en México se usa: "Pesco los lunes que caen entre semana" Todos los lunes están entre semana "Pesco solo los sábados que caen en fin de semana" Todos los sábados están en fin de semana
I don't think there's such thing in spanish language.
The joke in english language follows nicely because each week day ends in "y." However, in spanish language we have:
lunes, martes, miércoles, jueves y viernes.
so the joke in this case could be:
solo pesco en días que terminen en "s."
This doesn't apply to sábado y domingo, because of its terminations.
Para terminar el chiste de Ustanak:
Sólo pesco en días que terminen en s: lunes, martes, miércoles, jueves, viernes y feriados.
(OK, la frase es muy larga y la verdad no creo que nadie se ría).
