First of all, I am aware of this thread exploring “back in the day.” However, I feel that “back then” is slightly different.

I am wondering if there is a considerable difference in meaning and/or use between the following (the last one seems to be scarce):

  • en ese entonces
  • en aquel entonces
  • en aquel momento
  • en aquella época
  • a la sazón
  • 1
    back in the day is being used a lot now. This was not always the case. It is used to refer to something that occurred a few years before. It used to mean a long time ago in a person's life. Back then and back in the day are almost synonymous in contemporary speech. The original usage was: back in the day of horse drawn wagons. Both mean the same thing. And they are all the same as: at that time.
    – Lambie
    Commented May 4, 2019 at 23:00
  • 2
    @Lambie - to me, the difference between "back then" and "back in the day" is that the latter expresses nostalgia, and the former might or might not carry that feeling. Commented May 5, 2019 at 6:58
  • @Lambie in that vein, I feel that “back then” only references a (more or less) specific time, while “back in the day” has that meaning plus the meaning of “(at some point) in the past”. Talking about the first one here. Commented May 5, 2019 at 7:35
  • 1
    @aparente001 back in the day does not necessarily involved nostalgia; "Back in the day, we had a lot of shootings in this neighborhood."
    – Lambie
    Commented May 5, 2019 at 15:18
  • 1
    You are not understanding me: that fondness thing is only at times: Back in the day, there were many rats in the sewers in this neighborhood. No fondness for rats, right? The Free Dictionary does not give the two ideas that I have given above. A "contemporary" use of it and a prior use of it.
    – Lambie
    Commented May 7, 2019 at 15:18

2 Answers 2


My answer is written from the point of view of a transplant living (previously) in Mexico.

  • en ese entonces, en aquel entonces: I would use these in conversation, to clarify that at a certain point in time, I wasn't aware of such-and-so yet. "¿Cómo podíamos entregar ese laboratorio a tiempo si en el momento de hacer el experimento, la maestra no nos había dado el formato bien bien?" "No, pues no, en aquel entonces [en ese entonces] no nos había dicho todavía cómo había que hacer los informes de laboratorio para su clase."

  • en aquel momento, en ese momento: I would use this for an action that occurred (or didn't occur) at a more pinpointed time. Cenicienta salió corriendo cuando dieron las doce. En ese momento el príncipe se dio cuenta que se había enamorado de ella, y empezó a hacer sus planes para buscar a la joven por todas partes del reino.

    Personally I tend to combine like this: aquel entonces, ese momento, maybe because "ese entonces" has the final E gliding into the initial E, which is a little troublesome (for me at least). For the same reason I tend not to say "esa época" as much as "aquella época."

  • en aquella época: this is for a general description of a period of time, whether historical or in a person's life. En aquella época se permitía fumar en el cine.

  • a la sazón: I see that dictionaries give a meaning similar to the above phrases. But previously, I only knew this with the meaning "concurrently," "at the same time as" or "in addition to." The way I thought of it in my mind -- and this may be completely off base -- was that when you get a surprising coincidence, it feels sort of spicy. Example from linguee.com: La Comisión recibió a la sazón otras denuncias de obstáculos a la comercialización en Dinamarca de productos alimenticios con [...] | At the same time, other complaints were reaching the Commission denouncing obstacles to the marketing in Denmark of foodstuffs [...]


In Spanish we use este, ese, aquel to refer to things based on distance: este for the nearest one, aquel for the farthest, and ese for anything in between.
Because of this, time expressions using aquel seem farther in time than those using ese: En aquel entonces makes you think of something that happened centuries ago, while En ese entonces makes you think of something that happened when your parents or grandparents were young.

Also, momento is obviously more specific than época, so you would use one to talk about a very specific point in time and the other to talk about general events in the past.

And yes, a la sazón is barely used at all in conversation, but can be handy in written works to avoid repetition of this kind of temporal expressions.

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