It is the Fifth day of Paryushan Parv or Dash Lakshan Dharm.
Satya means Truth; If talking is not required, then do not talk. If it is required then only use the minimum of words, and all must be absolutely true. Talking disturbs the stillness of the mind. Consider the person who lies and lives in fear of being exposed. To support one lie he has to utter a hundred more. He becomes caught up in a tangled web of lies and is seen as untrustworthy and unreliable. Lying leads to an influx of paap karma.
Satya comes from the word sat, which means existence. Existence is a quality of the soul. Recognizing the soul's true nature as it really exists and taking shelter in the soul is practicing Satya Dharma.