The range of the spectrum of jhana is wide, just FYI. So many ways to develop them, aspects to make stronger or emphasize over others, ways to think of them, and a vast range of experiences within that vast landscape covered by the word jhana.
Definitions vary, and criteria for jhana are a hot-button political issue, but practically, any shift into non-ordinary meditative attention is going to have some jhanic elements to it, and it is just a question of how deep, how long, how steady, how clear, with what aspects emphasized, and the like, and that is a huge grey area of axes of development.
So, it is definitely possible to be walking around in states that have jhanic qualities, regardless of whether or not they meet some arbitrary definition of jhana, and it is very much possible to learn to shift into them very rapidly and sometimes very strongly with practice in daily life.
People seem to vary in terms of how much they are talented in this regard, but regardless of your inherent ability or proclivities, good training and repetition and hard work generally pays off for most, and so if you learn jhana, say, on retreat well, with repetition and resolutions and continued practice, many can get so they can replicate at least some version of those in daily life.
In my jhana-obsessed days (think late 90's to early 2000's), I got to the point that I could power-shift through the jhanas from 1-8 in about 10-15 minutes with a pretty high degree of depth and could even skip up to higher ones in a slightly lighter version without any setup at all just by closing my eyes and calling out the number in my mind and, with some energetic odd shudder, the whole system would shift into that way of perceiving things within few seconds. I hadn't practiced that way in quite a while, but some months ago when I wanted to see if I could still do that, within a few days of re-energizing those pathways there it all was again. Anyway, the take home point is that if you want them, go out and get them, and if you want them to be available in daily life, really give them attention and work that groove deep and you will find that they get much easier and are much closer to the surface, just like anything we really practice well.
The cycles of practice can interfere with jhanic ability sometimes, so if you are heavily into the Dark Night or some early new progress cycle, they might be farther away or not as clean, but come a Review cycle and they may be right back again...
