Nowadays, these days or today?

from English Grammar Today

We can use nowadays, these days or today as adverbs meaning ‘at the present time, in comparison with the past’:

I don’t watch TV very much nowadays. There’s so much rubbish on. It’s not like it used to be.

Young people nowadays don’t respect their teachers any more.

Warning:

Take care to spell nowadays correctly: not ‘nowdays’.

These days is more informal:

These days you never see a young person give up their seat for an older person on the bus. That’s what I was taught to do when I was a kid.

Pop singers these days don’t seem to last more than a couple of months, then you never hear of them again.

Today is slightly more formal:

Apartments today are often designed for people with busy lifestyles.

We can use today, but not nowadays or these days, with the possessive ’s construction before a noun, or with of after a noun. This use is quite formal:

Today’s family structures are quite different from those of 100 years ago.

The youth of today have never known what life was like without computers.

Warning:

We don’t use nowadays, these days or today as adjectives:

Cars nowadays/these days/today are much more efficient and economical.

Not: The nowadays cars / The these days cars / The today’s cars …

(“Nowadays, these days or today ?” from English Grammar Today © Cambridge University Press.)

http://dictionary.cambridge.org/grammar/british-grammar/nowadays-these-days-or-today