Miqsam said that Ibn `Abbas said that the Appointed Days are the days of Tashriq, four days: the day of the Sacrifice (10th of Dhul-Hijjah) and three days after that.
This opinion was also reported of Ibn `Umar, Ibn Az-Zubayr, Abu Musa, `Ata', Mujahid, `Ikrimah, Sa`id bin Jubayr, Abu Malik, Ibrahim An-Nakha`i, Yahya bin Abu Kathir, Al-Hasan, Qatadah, As-Suddi, Az-Zuhri, Ar-Rabi` bin Anas, Ad-Dahhak, Muqatil bin Hayyan, `Ata' Al-Khurasani, Malik bin Anas, and others. In addition, the apparent meaning of the following Ayah supports this opinion:
﴿ فَمَن تَعَجَّلَ فِى يَوۡمَيۡنِ فَلَآ إِثۡمَ عَلَيۡهِ وَمَن تَأَخَّرَ فَلَآ إِثۡمَ عَلَيۡهِۚ ﴾
(But whosoever hastens to leave in two days, there is no sin on him and whosoever stays on, there is no sin on him.)
So the Ayah hints to the three days after the day of Sacrifice.
﴿ وَٱذۡكُرُواْ ٱللَّهَ فِىٓ أَيَّامٍ۬ مَّعۡدُودَٲتٍ۬ۚ ﴾
(And remember Allah during the Appointed Days) directs remembering Allah upon slaughtering the animals, after the prayers, and by Dhikr (supplication) in general. It also includes Takbir and remembering Allah while throwing the pebbles every day during the Tashriq days. A Hadith that Abu Dawud and several others collected states:
إِنَّمَا جُعِلَ الطَّوَافُ بِالْبَيْتِ وَالسَّعْيُ بَيْنَ الصَّفَا وَالْمَرْوَةِ وَرَمْيُ الْجِمَارِ لإِقَامَةِ ذِكْرِ اللهِ عَزَّ وَجَلَّ
(Tawaf around the House, Sa`i between As-Safa and Al-Marwah and throwing the pebbles were legislated so that Allah is remembered in Dhikr.)
When mentioning the first procession (refer to 2:199) and the second procession of the people upon the end of the Hajj season, when they start to return to their areas, after they had gathered during the rituals and at the standing places, Allah said,
﴿ وَٱتَّقُواْ ٱللَّهَ وَٱعۡلَمُوٓاْ أَنَّڪُمۡ إِلَيۡهِ تُحۡشَرُونَ ﴾
(and obey Allah (fear Him), and know that you will surely be gathered unto Him.)
﴿ وَهُوَ ٱلَّذِى ذَرَأَكُمۡ فِى ٱلۡأَرۡضِ وَإِلَيۡهِ تُحۡشَرُونَ ﴾
(And it is He Who has created you on the earth, and to Him you shall be gathered back.) (23:79)
﴿ وَمِنَ ٱلنَّاسِ مَن يُعۡجِبُكَ قَوۡلُهُ ۥ فِى ٱلۡحَيَوٰةِ ٱلدُّنۡيَا وَيُشۡهِدُ ٱللَّهَ عَلَىٰ مَا فِى قَلۡبِهِۦ وَهُوَ أَلَدُّ ٱلۡخِصَامِ • وَإِذَا تَوَلَّىٰ سَعَىٰ فِى ٱلۡأَرۡضِ لِيُفۡسِدَ فِيهَا وَيُهۡلِكَ ٱلۡحَرۡثَ وَٱلنَّسۡلَۗ وَٱللَّهُ لَا يُحِبُّ ٱلۡفَسَادَ • وَإِذَا قِيلَ لَهُ ٱتَّقِ ٱللَّهَ أَخَذَتۡهُ ٱلۡعِزَّةُ بِٱلۡإِثۡمِۚ فَحَسۡبُهُ ۥ جَهَنَّمُۚ وَلَبِئۡسَ ٱلۡمِهَادُ • وَمِنَ ٱلنَّاسِ مَن يَشۡرِى نَفۡسَهُ ٱبۡتِغَآءَ مَرۡضَاتِ ٱللَّهِۗ وَٱللَّهُ رَءُوفُۢ بِٱلۡعِبَادِ ﴾
(204. And of mankind there is he whose speech may please you (O Muhammad), in this worldly life, and he calls Allah to witness as to that which is in his heart, yet he is the most quarrelsome of the opponents.) (205. And when he turns away (from you O Muhammad), his effort in the land is to make mischief therein and to destroy the crops and the cattle, and Allah likes not mischief). (206. And when it is said to him, "Fear Allah'', he is led by arrogance to (more) crime. So enough for him is Hell, and worst indeed is that place to rest!) (207. And of mankind is he who would sell himself, seeking the pleasure of Allah. And Allah is full of kindness to (His) servants.)