1) WARN - Entry 'east:28525' (bib/east.bib): Invalid format '2007-2008' of date field 'date' - ignoring
2) WARN - Entry 'east:5297' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
3) WARN - Entry 'east:5315' (bib/east.bib): Invalid format 'between 1076 and 1093' of date field 'date' - ignoring
4) WARN - Entry 'east:5158' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
5) WARN - Entry 'east:5363' (bib/east.bib): Invalid format '2nd half of the 11th century' of date field 'date' - ignoring
6) WARN - Entry 'east:5649' (bib/east.bib): Invalid format '2nd half of the 11th century' of date field 'date' - ignoring
7) WARN - Entry 'east:5440' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
8) WARN - Entry 'east:5022' (bib/east.bib): Invalid format '711' of date field 'date' - ignoring
9) WARN - Entry 'east:5132' (bib/east.bib): Invalid format '647' of date field 'date' - ignoring
10) WARN - Entry 'east:5152' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
11) WARN - Entry 'east:4998' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
12) WARN - Entry 'east:5137' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring
13) WARN - Entry 'east:5181' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring
14) WARN - Entry 'east:5403' (bib/east.bib): Invalid format 'beginning of the 14th century' of date field 'date' - ignoring
15) WARN - Entry 'east:5379' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring
16) WARN - Entry 'east:5029' (bib/east.bib): Invalid format '710' of date field 'date' - ignoring
17) WARN - Entry 'east:5163' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
18) WARN - Entry 'east:5013' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
19) WARN - Entry 'east:5038' (bib/east.bib): Invalid format '703' of date field 'date' - ignoring
20) WARN - Entry 'east:5342' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring
21) WARN - Entry 'east:5447' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
22) WARN - Entry 'east:5329' (bib/east.bib): Invalid format 'end of the 11th century' of date field 'date' - ignoring
23) WARN - Entry 'east:5352' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring
24) WARN - Entry 'east:5273' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
25) WARN - Entry 'east:5268' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
26) WARN - Entry 'east:5216' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
27) WARN - Entry 'east:5314' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring
28) WARN - Entry 'east:5387' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
29) WARN - Entry 'east:5389' (bib/east.bib): Invalid format 'before mid-11th century' of date field 'date' - ignoring
30) WARN - Entry 'east:5325' (bib/east.bib): Invalid format 'first half of the 12th century' of date field 'date' - ignoring
31) WARN - Entry 'east:5026' (bib/east.bib): Invalid format '648' of date field 'date' - ignoring
32) WARN - Entry 'east:5018' (bib/east.bib): Invalid format 'between 557 and 569' of date field 'date' - ignoring
33) WARN - Entry 'east:5100' (bib/east.bib): Invalid format '710' of date field 'date' - ignoring
34) WARN - Entry 'east:5215' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
35) WARN - Entry 'east:5051' (bib/east.bib): Invalid format '763' of date field 'date' - ignoring
36) WARN - Entry 'east:5239' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
37) WARN - Entry 'east:5247' (bib/east.bib): Invalid format 'between 1076 and 1093' of date field 'date' - ignoring
38) WARN - Entry 'east:5468' (bib/east.bib): Invalid format '2nd half of the 11th century' of date field 'date' - ignoring
39) WARN - Entry 'east:5380' (bib/east.bib): Invalid format 'between 1076 to 1093' of date field 'date' - ignoring
40) WARN - Entry 'east:5064' (bib/east.bib): Invalid format 'end of 11th century' of date field 'date' - ignoring
41) WARN - Entry 'east:5356' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring
42) WARN - Entry 'east:5266' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
43) WARN - Entry 'east:5323' (bib/east.bib): Invalid format 'between 1076 and 1093' of date field 'date' - ignoring
44) WARN - Entry 'east:5197' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
45) WARN - Entry 'east:5431' (bib/east.bib): Invalid format 'between 1076 and 1093' of date field 'date' - ignoring
46) WARN - Entry 'east:5362' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring
47) WARN - Entry 'east:5080' (bib/east.bib): Invalid format '657' of date field 'date' - ignoring
48) WARN - Entry 'east:5425' (bib/east.bib): Invalid format '2nd half of the 11th century' of date field 'date' - ignoring
49) WARN - Entry 'east:5384' (bib/east.bib): Invalid format 'beginning of the 9th century' of date field 'date' - ignoring
50) WARN - Entry 'east:5199' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring
51) WARN - Entry 'east:5507' (bib/east.bib): Invalid format 'end of the 11th century' of date field 'date' - ignoring
52) WARN - Entry 'east:5068' (bib/east.bib): Invalid format '711' of date field 'date' - ignoring
53) WARN - Entry 'east:5690' (bib/east.bib): Invalid format 'end of the 11th century' of date field 'date' - ignoring
Biblatex uses "iso8601-2 Extended Format specification level 1" for dates, but not all of the date fields in east.bib adhere to this standard. See sections 2.3.8 and 2.3.9 (http://mirror.kumi.systems/ctan/macros/latex/contrib/biblatex/doc/biblatex.pdf#page=38) for the date specification in Biblatex.
Currently, biber lists the following warnings:
1) WARN - Entry 'east:28525' (bib/east.bib): Invalid format '2007-2008' of date field 'date' - ignoring 2) WARN - Entry 'east:5297' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 3) WARN - Entry 'east:5315' (bib/east.bib): Invalid format 'between 1076 and 1093' of date field 'date' - ignoring 4) WARN - Entry 'east:5158' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 5) WARN - Entry 'east:5363' (bib/east.bib): Invalid format '2nd half of the 11th century' of date field 'date' - ignoring 6) WARN - Entry 'east:5649' (bib/east.bib): Invalid format '2nd half of the 11th century' of date field 'date' - ignoring 7) WARN - Entry 'east:5440' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 8) WARN - Entry 'east:5022' (bib/east.bib): Invalid format '711' of date field 'date' - ignoring 9) WARN - Entry 'east:5132' (bib/east.bib): Invalid format '647' of date field 'date' - ignoring 10) WARN - Entry 'east:5152' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 11) WARN - Entry 'east:4998' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 12) WARN - Entry 'east:5137' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring 13) WARN - Entry 'east:5181' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring 14) WARN - Entry 'east:5403' (bib/east.bib): Invalid format 'beginning of the 14th century' of date field 'date' - ignoring 15) WARN - Entry 'east:5379' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring 16) WARN - Entry 'east:5029' (bib/east.bib): Invalid format '710' of date field 'date' - ignoring 17) WARN - Entry 'east:5163' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 18) WARN - Entry 'east:5013' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 19) WARN - Entry 'east:5038' (bib/east.bib): Invalid format '703' of date field 'date' - ignoring 20) WARN - Entry 'east:5342' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring 21) WARN - Entry 'east:5447' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 22) WARN - Entry 'east:5329' (bib/east.bib): Invalid format 'end of the 11th century' of date field 'date' - ignoring 23) WARN - Entry 'east:5352' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring 24) WARN - Entry 'east:5273' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 25) WARN - Entry 'east:5268' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 26) WARN - Entry 'east:5216' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 27) WARN - Entry 'east:5314' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring 28) WARN - Entry 'east:5387' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 29) WARN - Entry 'east:5389' (bib/east.bib): Invalid format 'before mid-11th century' of date field 'date' - ignoring 30) WARN - Entry 'east:5325' (bib/east.bib): Invalid format 'first half of the 12th century' of date field 'date' - ignoring 31) WARN - Entry 'east:5026' (bib/east.bib): Invalid format '648' of date field 'date' - ignoring 32) WARN - Entry 'east:5018' (bib/east.bib): Invalid format 'between 557 and 569' of date field 'date' - ignoring 33) WARN - Entry 'east:5100' (bib/east.bib): Invalid format '710' of date field 'date' - ignoring 34) WARN - Entry 'east:5215' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 35) WARN - Entry 'east:5051' (bib/east.bib): Invalid format '763' of date field 'date' - ignoring 36) WARN - Entry 'east:5239' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 37) WARN - Entry 'east:5247' (bib/east.bib): Invalid format 'between 1076 and 1093' of date field 'date' - ignoring 38) WARN - Entry 'east:5468' (bib/east.bib): Invalid format '2nd half of the 11th century' of date field 'date' - ignoring 39) WARN - Entry 'east:5380' (bib/east.bib): Invalid format 'between 1076 to 1093' of date field 'date' - ignoring 40) WARN - Entry 'east:5064' (bib/east.bib): Invalid format 'end of 11th century' of date field 'date' - ignoring 41) WARN - Entry 'east:5356' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring 42) WARN - Entry 'east:5266' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 43) WARN - Entry 'east:5323' (bib/east.bib): Invalid format 'between 1076 and 1093' of date field 'date' - ignoring 44) WARN - Entry 'east:5197' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 45) WARN - Entry 'east:5431' (bib/east.bib): Invalid format 'between 1076 and 1093' of date field 'date' - ignoring 46) WARN - Entry 'east:5362' (bib/east.bib): Invalid format '800' of date field 'date' - ignoring 47) WARN - Entry 'east:5080' (bib/east.bib): Invalid format '657' of date field 'date' - ignoring 48) WARN - Entry 'east:5425' (bib/east.bib): Invalid format '2nd half of the 11th century' of date field 'date' - ignoring 49) WARN - Entry 'east:5384' (bib/east.bib): Invalid format 'beginning of the 9th century' of date field 'date' - ignoring 50) WARN - Entry 'east:5199' (bib/east.bib): Invalid format 'mid-11th century' of date field 'date' - ignoring 51) WARN - Entry 'east:5507' (bib/east.bib): Invalid format 'end of the 11th century' of date field 'date' - ignoring 52) WARN - Entry 'east:5068' (bib/east.bib): Invalid format '711' of date field 'date' - ignoring 53) WARN - Entry 'east:5690' (bib/east.bib): Invalid format 'end of the 11th century' of date field 'date' - ignoring