Sea Time/Land Time

The answer lies in the distinction between sea time and land time, or the nautical day and the civil day. From the late 17th century (at least) until the 1920s, the nautical day began at noon on the previous day (according to civil time). Noon was when the latitude and longitude of a ship were calculated, and bearings and distances were taken, and it became conventional for the nautical day to commence at that time.

So when the Sirius’s (and Bradley’s) journal read 3pm on 27th of January, it was actually 3pm on the 26th by land time. Bradley’s sketch is recording the fact that the last of the First Fleet made their way into Port Jackson after noon on the 26th.

The 12 hour difference between sea and land time created a number of problems. When a ship arrived in port, it was necessary to transition from nautical to civil time, resulting in a day which lasted only 12 hours, and another on sailing which lasted 36. These transitions were commonly mentioned in the ships' logs: thus the journal of the First Fleet ship, the Borrowdale, reports on sailing from the Spithead on the 12th of May 1788, ‘This days Work 36 hours’.[1]

If vessels were visiting a small port where there would be no interaction with shore, or if they were only going to be in port briefly, the log might not change. This left room for different practices on different ships that were sailing as part of a convoy.[2]

And in their personal journals, some mariners and passengers might make the shift to the nautical day, while others would not. Admiral Nelson kept civil time in his private journal for the Battle of Trafalgar, while the logs and journals of the Victory were kept in nautical.[3]

This distinction between sea time and land time explains many of the timing differences among the various journals for the First Fleet, 'though not all: in one case, the journal keeper seems to have made mistakes when writing up the fair copy after the event.

So, looking at the First Fleet - the Supply made her way into Botany Bay on the afternoon of the 18th of January (by land time), which according to her log was the first part of the 19th (by sea time). She was followed by the Alexander, Scarborough and Friendship on the morning of the 19th (the first part of the day by land time, and the second by sea). The Supply and the other three ships had arrived in Botany Bay on the same nautical day, but on different civil days.

She sailed into Port Jackson in the first part of the 26th, and Phillip went ashore early in the second part of that day, according to sea time; but according to civil time, they entered the harbour on the afternoon of the 25th and went ashore at daybreak the next morning. The rest of the fleet entered Port Jackson on the first part of the 27th by sea time, and the convicts and marines were sent ashore on the second part of that same day: by land time, they entered the harbour on the afternoon of the 26th and went ashore on the 27th.

Philip Gidley King’s journal for the Supply (the version held by the Royal Collections Trust at Windsor) made the change from the layout of a ship’s log to the narrative form used when vessels were in port, on the 19th (that is, the afternoon of the 18th by land time). But the change from sea time to land time was not made until the 20th. King’s entry for Saturday the 19th reads ‘Nautical Day’ and that of the 20th, ‘Natural Day’.

The four known journals for the Sirius all remained on sea time until they were finished over the course of 1788, although they changed from a sea journal to the narrative form on the day of their arrival in Botany Bay.

The log of the Alexander does not report the shift from sea time to land time, but they had changed across by the 26th, since the entry that day commences at 10am in Botany Bay, and reports that by 4pm, they had arrived at the entrance to Port Jackson.

The Prince of Wales and the Scarborough also shifted to land time at Botany Bay without reporting the change. The Friendship concluded her entry for the 19th of January, the day she came into Botany Bay, with the words: ‘So ends the Sea Journal’, reporting events thereafter in civil time.

The log of the Charlotte, on the other hand, reports that she came to in five fathoms of water in Port Jackson at 7.15 pm on the 27th of January – she was still on sea time. The Golden Grove also remained on nautical time until the 27th.

The surviving journal of the Lady Penrhyn was written up later, with the copyist attempting to convert the journal to land time: he got it wrong, presumably because he was not familiar with the relationship between the two systems. The log is on sea time, commencing the account for the 26th with events in the afternoon and concluding at noon the next day. But he shifted the timing back 24 hours not 12, so he has the fleet arriving off Sydney Cove on the afternoon of the 26th, which is correct by land time, and warping into the cove the same nautical day, when that occurred on the morning of the 27th by land time.

Sufficiently confused ?

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[1] ‘A Journal of a Voyage in the Borrowdale’, UK National Archives, ADM51/4375.

[2] Clive Wilkinson, ‘British Logbooks in UK Archives in 17th-19th Centuries’, MS, Climate Research Unit, University of East Anglia, February 2009, p.22.

[3] Henry Harries, ‘Nautical Time’, The Mariner’s Mirror, (1928) 14:4, pp.364-370.