A method of checking a new calendar entry in a calendar application of a handheld electronic device, said calendar application having a plurality of existing calendar entries, said calendar application having a calendar cache associated therewith, said calendar cache including a first subset of said existing calendar entries falling within a first date range, the method comprising steps of: receiving information relating to said new calendar entry, said information including at least one of a date, a start time and an end time of said new calendar entry; determining whether said date falls within said first date range of said calendar cache; if said date falls within said first date range: (i) examining said calendar cache and determining whether said new calendar entry directly conflicts with one of said existing calendar entries in said first subset of said existing calendar entries using said information, and (ii) providing a conflict notification if said new calendar entry directly conflicts with one of said existing calendar entries in said first subset of said existing calendar entries; and if said date falls outside of said first date range: (i) updating said calendar cache to create an updated calendar cache by replacing said first subset of said existing calendar entries with a second subset of said existing calendar entries falling within a second date range, said second date range covering a predetermined time period including said date, (ii) examining said updated calendar cache and determining whether said new calendar entry directly conflicts with one of said existing calendar entries in said second subset of said existing calendar entries using said information, and (iii) providing a conflict notification if said new calendar entry directly conflicts with one of said existing calendar entries in said second subset of said existing calendar entries. receiving information relating to said new calendar entry, said information including at least one of a date, a start time and an end time of said new calendar entry; determining whether said date falls within said first date range of said calendar cache; if said date falls within said first date range: (i) examining said calendar cache and determining whether said new calendar entry directly conflicts with one of said existing calendar entries in said first subset of said existing calendar entries using said information, and (ii) providing a conflict notification if said new calendar entry directly conflicts with one of said existing calendar entries in said first subset of said existing calendar entries; and if said date falls outside of said first date range: (i) updating said calendar cache to create an updated calendar cache by replacing said first subset of said existing calendar entries with a second subset of said existing calendar entries falling within a second date range, said second date range covering a predetermined time period including said date, (ii) examining said updated calendar cache and determining whether said new calendar entry directly conflicts with one of said existing calendar entries in said second subset of said existing calendar entries using said information, and (iii) providing a conflict notification if said new calendar entry directly conflicts with one of said existing calendar entries in said second subset of said existing calendar entries.