1991/1/1: 010191 = 010:191 = each is palindrome
1991/1/2: 020191 = 020:191 = each is palindrome
1991/1/3: 030191 = 030:191 = each is palindrome
1991/1/3: 1391 = 13:91 = integer ratio of 1 to 7
1991/1/3: 9113 = 91:13 = integer ratio of 7 to 1
1991/1/4: 040191 = 040:191 = each is palindrome
1991/1/5: 050191 = 050:191 = each is palindrome
1991/1/6: 060191 = 060:191 = each is palindrome
1991/1/6: 1691 = 180 deg rotationally symmetric
1991/1/6: 91016 = 180 deg rotationally symmetric
1991/1/6: 9116 = 180 deg rotationally symmetric
1991/1/7: 070191 = 070:191 = each is palindrome
1991/1/8: 080191 = 080:191 = each is palindrome
1991/1/9: 090191 = 090:191 = each is palindrome
1991/1/9: 1991 = palindrome
1991/1/9: 91019 = palindrome
1991/1/9: 9119 = palindrome
1991/1/9: 9191 = cyclic permutation symmetric
1991/1/10: 01101991 = 0110:1991 = each is palindrome
1991/1/10: 10011991 = 1001:1991 = each is palindrome
1991/1/10: 19910110 = 1991:0110 = each is palindrome
1991/1/16: 16191 = 180 deg rotationally symmetric
1991/1/16: 91116 = 180 deg rotationally symmetric
1991/1/18: 011891 = 011:891 = integer ratio of 1 to 81
1991/1/19: 19191 = palindrome
1991/1/19: 91119 = palindrome
1991/1/30: 013091 = 013:091 = integer ratio of 1 to 7
1991/1/30: 910130 = 910:130 = integer ratio of 7 to 1
1991/2/1: 020191 = 020:191 = each is palindrome
1991/2/19: 19291 = palindrome
1991/2/19: 91219 = palindrome
1991/2/20: 02201991 = 0220:1991 = each is palindrome
1991/2/20: 19910220 = 1991:0220 = each is palindrome
1991/2/20: 20021991 = 2002:1991 = each is palindrome
1991/3/1: 030191 = 030:191 = each is palindrome
1991/3/1: 1391 = 13:91 = integer ratio of 1 to 7
1991/3/19: 19391 = palindrome
1991/3/19: 91319 = palindrome
1991/3/30: 03301991 = 0330:1991 = each is palindrome
1991/3/30: 19910330 = 1991:0330 = each is palindrome
1991/3/30: 30031991 = 3003:1991 = each is palindrome
1991/4/1: 040191 = 040:191 = each is palindrome
1991/4/19: 19491 = palindrome
1991/4/19: 91419 = palindrome
1991/5/1: 050191 = 050:191 = each is palindrome
1991/5/19: 19591 = palindrome
1991/5/19: 91519 = palindrome
1991/6/1: 060191 = 060:191 = each is palindrome
1991/6/1: 1691 = 180 deg rotationally symmetric
1991/6/16: 1661991 = 180 deg rotationally symmetric
1991/6/19: 19691 = palindrome
1991/6/19: 91619 = palindrome
1991/7/1: 070191 = 070:191 = each is palindrome
1991/7/19: 19791 = palindrome
1991/7/19: 91719 = palindrome
1991/8/1: 080191 = 080:191 = each is palindrome
1991/8/18: 081891 = 081:891 = integer ratio of 1 to 11
1991/8/19: 19891 = palindrome
1991/8/19: 91819 = palindrome
1991/9/1: 090191 = 090:191 = each is palindrome
1991/9/1: 1991 = palindrome
1991/9/1: 9191 = cyclic permutation symmetric
1991/9/9: 199199 = cyclic permutation symmetric
1991/9/9: 991991 = cyclic permutation symmetric
1991/9/10: 091091 = cyclic permutation symmetric
1991/9/10: 910910 = cyclic permutation symmetric
1991/9/19: 1991991 = palindrome
1991/9/19: 19991 = palindrome
1991/9/19: 91919 = palindrome
1991/10/1: 01101991 = 0110:1991 = each is palindrome
1991/10/1: 10011991 = 1001:1991 = each is palindrome
1991/10/1: 19911001 = 1991:1001 = each is palindrome
1991/10/1: 911001 = 911:001 = integer ratio of 911 to 1
1991/10/9: 091091 = cyclic permutation symmetric
1991/10/11: 101191 = 101:191 = each is palindrome
1991/11/6: 91116 = 180 deg rotationally symmetric
1991/11/9: 91119 = palindrome
1991/11/10: 101191 = 101:191 = each is palindrome
1991/11/11: 11111991 = 1111:1991 = each is palindrome
1991/11/11: 111191 = 111:191 = each is palindrome
1991/11/11: 19911111 = 1991:1111 = each is palindrome
1991/11/12: 121191 = 121:191 = each is palindrome
1991/11/13: 131191 = 131:191 = each is palindrome
1991/11/14: 141191 = 141:191 = each is palindrome
1991/11/15: 151191 = 151:191 = each is palindrome
1991/11/16: 161191 = 180 deg rotationally symmetric
1991/11/16: 161191 = 161:191 = each is palindrome
1991/11/16: 911116 = 180 deg rotationally symmetric
1991/11/17: 171191 = 171:191 = each is palindrome
1991/11/18: 181191 = 181:191 = each is palindrome
1991/11/19: 191191 = palindrome
1991/11/19: 191191 = cyclic permutation symmetric
1991/11/19: 191191 = 191:191 = each is palindrome
1991/11/19: 911119 = palindrome
1991/12/11: 121191 = 121:191 = each is palindrome
1991/12/21: 12211991 = 1221:1991 = each is palindrome
1991/12/21: 19911221 = 1991:1221 = each is palindrome
1991/12/21: 21121991 = 2112:1991 = each is palindrome
1991/12/29: 291291 = cyclic permutation symmetric