Have you ever written a diary or a journal? Diurnal prose and register variation

The terms diary and journal are often used interchangeably: both types of text are written in autobiographical persona and are associated with "daily records of events" (OED); they are personal "modes of diurnal narrative" (Sherman 1996).
However, the situational context in which the texts are produced is not identical. Situational characteristics, including participants, channel, setting, communicative purpose and topic, are one of the three major components that describe registers in Biber & Conrad's (2009) framework for analysing register variation. This paper will apply this framework to the text excerpts compiled in the historical corpus ARCHER (1650-1999) in an attempt to pinpoint the similarities and differences between diaries and journals in a systematic way. It will be argued that, while a number of parameters are shared, there are also important differences that favour their classification into two separate registers