Past tenses of Neoslavonic verbs are very easy and regular. There is only one pattern for all verbs (except for 3 irregular verbs byti = to be, iti = to go, jasti = to eat). This pattern is based on the infinitive.
Neoslavonic (as well as spoken Slavic) operates past tenses with the so called L-participle. It is a special form of indeclinable verbal adjective made from the infinitive.
děla-ti → děla-l, děla-la, děla-lo, děla-li (to do)
pisa-ti → pisa-l, pisa-la, pisa-lo, pisa-li (to write)
vidě-ti → vidě-l, vidě-la, vidě-lo, vidě-li (to see)
peč-ti → pek-l, pek-la, pek-lo, pek-li (to bake)
mož-ti → mog-l, mog-la, mog-lo, mog-li (to can)
simple past tense
The simple past tense is formed in a similar way as the L-participle.
děla-ti → děla-h, děla-še, děla-še, děla-hom, děla-ste, děla-hu (to do)
pisa-ti → pisa-h, pisa-še, pisa-še, pisa-hom, pisa-ste, pisa-hu (to write)
peč-ti → peč-e-h, peč-e-še, peč-e-še, peč-e-hom, peč-e-ste, peč-e-hu (to bake)
The foregoing simple past tense forms are found in the past tenses of Croatian, Serbian, Montenegrin, (Slavo) Macedonian and Bulgarian and were in all Slavic languages in the past. They are not, however, found in the modern Western Slavic and Eastern Slavic languages except Sorbian.
composed past tense = prior present tense
As noted above, the Western Slavic and Eastern Slavic languages do not use the simple past tense (-hu, -še , ...). Instead, they use the composed past tense made by the combination of the verb byti (to be) in the present tense and the L-participle in corresponding personal form (m. or f. or n. or pl.).
Jesi li pisala pismo? Did You (f.) write a letter?
Ne, on je pisal to pismo. No, he did write this letter.
If you use the past form of the verb byti (to be) instead of the present form, you will create the "prior past tense".
Běše li pisala pismo? Had you (f.) written a letter?
Ne, on běše pisal to pismo. No, he had written this letter.
symmetric system of Neoslavonic present and past tenses
If we do not assume a simplified system with only one past tense (either simple or composed), we can define the complex symmetric system of four tenses in two time levels: the present level and the past level.
Example of the present time level:
Hvalime Vas, že jeste razdělili otpad. Thank you for sorting waste. - thanking = present, sorting = prior-present.
The same example moved to the past time level:
Hvalihom Vas, že běste razdělili otpad. We did thank you for sorting waste. - thanking = past, sorting = prior-past.
It is obvious, that the relationship between thanking and sorting is the same in both examples: Sorting first, thanking after.