Remover o ponto na data (ou escapar com \. ) resolveu o erro no meu caso.
Veja: link
Eu sou novo no RStudio e no RMarkdown. Quando tentei fazer o meu primeiro documento pdf no Rstudio, recebi a seguinte mensagem:
processing file: Preview-4cef6f7763df.Rmd
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ordinary text without R code
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label: unnamed-chunk-1
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ordinary text without R code
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label: unnamed-chunk-2 (with options)
List of 1
$ echo: logi FALSE
cropping ./Preview-4cef6f7763df_files/figure-latex/unnamed-chunk-2-1.pdf
PDFCROP 1.38, 2012/11/02 - Copyright (c) 2002-2012 by Heiko Oberdiek.
==> 1 page written on './Preview-4cef6f7763df_files/figure-latex/unnamed-chunk-2-1.pdf'.
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ordinary text without R code
/usr/lib/rstudio/bin/pandoc/pandoc Preview-4cef6f7763df.utf8.md --to latex --from markdown+autolink_bare_uris+ascii_identifiers+tex_math_single_backslash-implicit_figures --output Preview-4cef6f7763df.pdf --template /home/klemen/R/i686-pc-linux-gnu-library/3.0/rmarkdown/rmd/latex/default.tex --highlight-style tango --latex-engine pdflatex --variable 'geometry:margin=1in'
output file: Preview-4cef6f7763df.knit.md
! Incomplete \iffalse; all text was ignored after line 110.
<inserted text>
\fi
<*> /tmp/tex2pdf.2746/input.tex
! ==> Fatal error occurred, no output PDF file produced!
Transcript written on /tmp/tex2pdf.2746/input.log.
pandoc: Error producing PDF from TeX source
Error: pandoc document conversion failed with error 43
Execution halted
Eu realmente não sei como consertar isso. Alguém pode ajudar? Obrigado.