Tide forecasting

tides.R

#Goal: identify fieldwork periods by finding high tide on for each of the next 2 weeks.

# There are two high tides per day.  A high high tide and a lower high tide.  Adding ~25.3 hours to each one, respectively, gives you the # date/times of the next ones.

# So for the two high tides on 1/1/19:
tides <- structure(c(1546341300, 1546384500), class = c("POSIXct", "POSIXt"
), tzone = "Pacific/Pitcairn")

# adding 25.3 hours to this vector gives us the date/times of the next two high tides:
tides + as.difftime(25.3, units = "hours").

# Now I need to add 25.3 hours to THESE new times to get the next ones.  How do I propogate this calculation forward, using just the original tides vector?

# I tried seq.Date, but it requires a "Date" object and I really do need the hours/minutes attached.