[Machine] Hudhaifah began fasting after the sun had set.  

أَنَّ حُذَيْفَةَ ؓ بَدَا لَهُ الصَّوْمُ بَعْدَمَا زَالَتِ الشَّمْسُ فَصَامَ  

[Machine] He is not considered a fasting person until he intends to fast before the sunset. As for us, we say that the voluntary fast is whenever one intends to fast.  

أَنَّهُ لَا يَكُونُ صَائِمًا حَتَّى يَنْوِيَ الصَّوْمَ قَبْلَ زَوَالِ الشَّمْسِ وَأَمَّا نَحْنُ فَنَقُولُ الْمُتَطَوِّعُ بِالصَّوْمِ مَتَى شَاءَ نَوَى الصِّيَامَ