In Digambar Jain tradition:

• Ṣaṭkhaṅḍāgama (Shatkhandagam) is older
• Mūlācāra (Mulāchār) is later

Very simple timeline (approximate):

1. Ṣaṭkhaṅḍāgama

- Based on the teachings of Āchārya Dharasena (1st century CE) - Written down by Āchārya Puṣpadanta and Bhūtabali - Considered one of the earliest and most ancient Digambar āgamas

1. Mūlācāra

- Composed by Āchārya Vattakera - Generally placed around 2nd century CE (after Shatkhandagam) - Focuses mainly on ācāra (conduct) of Digambar monks

So, Shatkhandagam is older than Mulachar.