The crawler report provided by Google Webmaster Tools does not provide data points beyond the past 90 days and it would be fairly difficult to maintain accurate records given the crawl rate data that is made available.
The data is actually embedded in the chart image URL's chd
parameter using the simple encoding scheme described in the Data Format document for the Google Charts API.
It is possible to extract the data (included JS functions culled from Google's documentation) but the data is normalized and, without the context of the high and low crawl rate figures, it wouldn't be particularly useful for tracking crawl rate over time.
/**
* number encoding map
*/
var SIMPLE_MAP='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
/**
* simpleDecoding function from
* URL: http://code.google.com/apis/chart/image/docs/data_formats.html
*/
function simpleDecoding(val) {
if (val.length != 1 || val == "_") {
return "";
}
var decodedVal = SIMPLE_MAP.indexOf(val.charAt(0));
if (decodedVal < 0) {
alert("Invalid decoding character.");
return "";
}
return decodedVal;
}
/**
* ... and decode a whole string
*/
function simpleDecode(val) {
var output = '';
for ( i = 0; i < val.length; i++ ) {
output += " "+simpleDecoding(val.charAt(i));
}
return output;
}