Here’s an example of the time phrase that means the person is at the age of 20-29:
I‘m not even in my twenties anymore.
This phrase is B2 in the English Vocabulary Profile:
(be) in your eighties
to be aged between 80 and 89the eighties
the years from 1980-1989
A search in iWeb corpus for:
_I _A _MC2
1 IN THE 1980S 57549
2 IN THE 1970S 56687
3 IN THE 1960S 49883
4 IN THE 1990S 45235
5 IN THE 1950S 40646
6 IN THE 1930S 28628
7 IN THE 1920S 22817
8 IN THE 80S 20687
9 IN THE 90S 18171
10 IN THE 70S 17104
11 IN THE 1940S 16073
12 OF THE 1960S 12811
13 IN THE 60S 12789
14 OF THE 1980S 11083
15 OF THE 1970S 10148
16 OF THE 1990S 9090
17 IN THE 1800S 8364
18 OF THE 1950S 7878
19 IN THE 50S 7757
20 DURING THE 1980S 7662
21 IN THE MID-1990S 7614
22 IN THEIR 20S 7596
23 OF THE 1930S 7408
24 DURING THE 1970S 6421
25 DURING THE 1960S 6215
26 OF THE 80S 6061
27 DURING THE 1990S 6022
28 FROM THE 1960S 5964
29 IN THE 1880S 5765
30 FROM THE 1950S 5668
31 DURING THE 1950S 5249
32 FROM THE 1970S 5248
33 OF THE 1920S 5223
34 IN THE SIXTIES 5085
35 OF THE 90S 5024
36 IN THE 1890S 4998
37 IN THE 2000S 4529
38 IN THE 1870S 4440
39 FROM THE 1980S 4313
40 IN THE 1860S 4305
41 OF THE 70S 4222
42 IN THE SEVENTIES 4221
43 IN THE 1850S 4183
44 DURING THE 1930S 4172
45 OF THE 60S 4107
46 IN THE EIGHTIES 4053
47 IN THEIR 30S 4013
48 FROM THE 1930S 3999
49 FROM THE 80S 3877
50 IN THE 80 3858
51 IN MY 20S 3608
52 DURING THE 1920S 3569
53 IN THE TENS 3475
54 FROM THE 1920S 3448
55 IN THE 1830S 3441
56 IN THE 40S 3386
57 IN THE 1840S 3346
58 FROM THE 70S 3316
59 IN THE 1970 3294
60 IN THE 1700S 3293
61 IN THE 30S 3263
62 IN HIS 20S 3172
63 IN THE 1980 3167
64 IN THEIR 40S 3046
65 IN THE 70 3029
66 IN THE 1960 3015
67 IN THE MID-90S 2969
68 IN THE 90 2962
69 IN THE NINETIES 2921
70 TO THE 1970S 2845
71 FROM THE 1940S 2796
72 OF THE 1940S 2788
73 FROM THE 60S 2739
74 IN THE FIFTIES 2662
75 IN THEIR TWENTIES 2662
76 OF THE SIXTIES 2636
77 IN THE 1950 2605
78 IN THE MID-2000S 2577
79 TO THE 1980S 2574
80 TO THE 1960S 2559
81 IN THE 20S 2556
82 IN THEIR 50S 2523
83 FROM THE 90S 2489
84 IN THE 1600S 2425
85 OF THE 2000S 2413
86 IN HIS 30S 2310
87 IN YOUR 20S 2310
88 TO THE 1950S 2301
89 IN THE 1990 2212
90 FROM THE 1990S 2204
91 BY THE 1980S 2130
92 BY THE 1970S 2113
93 IN THE 1930 2086
94 IN THE 1820S 2082
95 IN MY TWENTIES 2081
96 BY THE 1960S 2051
97 IN THE MID-1800S 2036
98 DURING THE 1940S 1963
99 OF THE 50S 1941
100 IN THE 60 1904