Shiva Purana
अन्येषां कालमानं च कालस्य कलना न हि ॥ महाकालस्स्वयं साक्षान्महाकालीसमाश्रितः ॥ २५॥
Restriction of time is for others and not for Rudra. He is Mahākāla himself associating with Mahākālī.
english translation
anyeSAM kAlamAnaM ca kAlasya kalanA na hi ॥ mahAkAlassvayaM sAkSAnmahAkAlIsamAzritaH ॥ 25॥
hk transliteration by Sanscript