Shiva Purana
नाडी यदा च वहति त्रयोदशदिनावधि ॥ सम्वत्सरं भवेत्तस्य चतुर्मासाः प्रकीर्तिताः ॥ ५९॥
And when the vein carries for thirteen days. It is said to be a year and four months.
english translation
nADI yadA ca vahati trayodazadinAvadhi ॥ samvatsaraM bhavettasya caturmAsAH prakIrtitAH ॥ 59॥
hk transliteration by Sanscript