Since there is no equivalent of AM or PM in Hindi we have to mention the time of the day along with the specific clock time. For example if we have to say 3 AM, the Hindi equivalent will be रात के/में तीन बजे which literally means 3 o'clock of/in night.

English Hindi Transliteration Notes
Now अब ab
Right Now अभी abhī
Later बाद में bād mēṃ
Then फिर phir
Before पहले pêhlē
After बाद bād
Morning सुबह/सवेरा subah/savērā savērā represents 04:00-05:59, subaha represents 06:00-11:59
Early Morning सुबह-सुबह subah-subah
Day दिन din also represents 04:00-19:59, but cannot follow time words.
Afternoon दोपहर dopêhêr
Evening शाम/संध्या śām/saṃdhyā saṃdhyā is mostly used in literary contexts, śām represents 16:00-20:00.
Night रात rāt represents 20:00-04:00

Clock time

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English Hindi Transliteration
1 AM रात के एक बजे rāt kē ēk bajē
7 AM सुबह के सात बजे subah kē sāt bajē
2 PM दोपहर के दो बजे dopêhêr kē do bajē
6 PM शाम के छै बजे śām kē chē bajē
7 PM शाम के सात बजे śām kē sāt bajē
8 PM रात के आठ बजे rāt kē āṭh bajē
9 PM रात के नौ बजे rāt kē nau bajē
midnight आधी रात ādhī rāt
Half past साढे sār̥hē
Half past 6 (6:30) साढे ६ (६:३०) sār̥hē 6
Quarter until पौने paunē
Quarter until 4 (3:45) पौने ४ (३:४५) paunē 4
Quarter past सवा savā
Quarter past 9 (9:15) सवा ९ (९:१५) savā 9
20 minutes past 8 (8:20) ८ बजकर २० मिनट (८:२०) 8 bajkar 20 minêṭ
12 minutes past 3 (3:12) ३ बजकर १२ मिनट (३:१२) 3 bajkar 12 minêṭ
7 minutes to 10 (9:53) १० बजने को ७ मिनट (९:५३) 10 bajnē ko 7 minêṭ

There are two exceptions to the Half past. Half past one (1:30) is डेढ़ (ḍēr̥h) and half past 2 (2:30) is ढाई (ḍhāī). A fun way to remember their order would be 'Unless you dare (Let's say this represents डेढ़) you die (and this represents ढाई). Voila!