It depends if all your logs are time-stamped and the format of the time stamp, but if the latter is in the form YYYY-MM-DD HH:MM:SS then you could use utilities such as "cat" and "sort" under Linux:
For more complex cases, you'd need to write some Perl, Python (or any other scripting language) program; taking into account your time stamp format specificities (such as inverted MM/DD/YYYY in English speaking countries, or AM/PM issues in 12 hours format).