diff --git a/autoload/nuwiki/diary.vim b/autoload/nuwiki/diary.vim
index acfebea..55acc25 100644
--- a/autoload/nuwiki/diary.vim
+++ b/autoload/nuwiki/diary.vim
@@ -3,6 +3,33 @@
 
 " ===== Calendar-Vim Integration =====
 
+" The wiki index (0-based) of the most recently entered wiki buffer. The
+" calendar shows / creates diary entries for this wiki, so opening the calendar
+" while editing `ifood_wiki` diaries into ifood_wiki — not always the first
+" wiki. Updated by the BufEnter autocmd in plugin/nuwiki.vim; defaults to 0.
+" (The LSP-driven diary commands already follow the current buffer via its URI;
+" this mirrors that for the VimL calendar-vim callbacks.)
+let s:current_wiki_idx = 0
+
+" Record the wiki that owns `file` as the current one. Called on entering a
+" wiki buffer. No-op when the file is under no configured wiki.
+function! nuwiki#diary#track_wiki(file) abort
+  let l:file = fnamemodify(a:file, ':p')
+  if empty(l:file)
+    return
+  endif
+  let l:n = 0
+  for l:w in nuwiki#commands#wiki_list()
+    let l:root = fnamemodify(expand(l:w.root), ':p')
+    if l:root[len(l:root) - 1:] !=# '/' | let l:root .= '/' | endif
+    if l:file[: len(l:root) - 1] ==# l:root
+      let s:current_wiki_idx = l:n
+      return
+    endif
+    let l:n += 1
+  endfor
+endfunction
+
 " Function: nuwiki#diary#calendar_action(day, month, year, week, dir)
 " Called by calendar-vim when user presses Enter on a date.
 " day/month/year are numeric integers; dir is 'V' for a vertical split (any
@@ -12,8 +39,8 @@ function! nuwiki#diary#calendar_action(day, month, year, week, dir) abort
   " Build YYYY-MM-DD from the parts passed by calendar-vim
   let l:date_str = printf('%04d-%02d-%02d', a:year, a:month, a:day)
 
-  " Get wiki configuration for the first wiki (index 0)
-  let l:c = s:wiki_cfg(0)
+  " Wiki of the buffer the calendar was opened from (falls back to the first).
+  let l:c = s:wiki_cfg(s:current_wiki_idx)
 
   " Construct file path: {root}/{diary_rel}/{YYYY-MM-DD}.{ext}
   let l:file_path = l:c.root . '/' . l:c.diary_rel . '/' . l:date_str . l:c.ext
@@ -62,8 +89,8 @@ function! nuwiki#diary#calendar_sign(day, month, year) abort
   " Build YYYY-MM-DD from the parts passed by calendar-vim
   let l:date_str = printf('%04d-%02d-%02d', a:year, a:month, a:day)
 
-  " Get wiki configuration for the first wiki (index 0)
-  let l:c = s:wiki_cfg(0)
+  " Wiki of the buffer the calendar was opened from (falls back to the first).
+  let l:c = s:wiki_cfg(s:current_wiki_idx)
 
   " Construct expected file path
   let l:file_path = l:c.root . '/' . l:c.diary_rel . '/' . l:date_str . l:c.ext
diff --git a/development/tests/test-calendar-vim.vim b/development/tests/test-calendar-vim.vim
index d50dabc..435c704 100644
--- a/development/tests/test-calendar-vim.vim
+++ b/development/tests/test-calendar-vim.vim
@@ -89,6 +89,24 @@ call s:record(winnr('$') == s:wins_before - 1, 'action.window_count_decremented'
 call s:record(&filetype ==# 'vimwiki', 'action.sets_filetype',
       \ 'filetype=' . &filetype)
 
+" ===== calendar follows the current wiki (multi-wiki) =====
+" Two wikis, each with its own diary entry. track_wiki() (driven by the
+" BufEnter autocmd in real use) switches which wiki the calendar reads.
+let s:wA = tempname() | call mkdir(s:wA . '/diary', 'p')
+let s:wB = tempname() | call mkdir(s:wB . '/diary', 'p')
+call writefile(['a'], s:wA . '/diary/2026-06-02.wiki')
+call writefile(['b'], s:wB . '/diary/2026-06-10.wiki')
+let g:nuwiki_wikis = [{'root': s:wA}, {'root': s:wB}]
+
+call nuwiki#diary#track_wiki(s:wA . '/index.wiki')
+call s:record(nuwiki#diary#calendar_sign(2, 6, 2026) ==# '*', 'track.wikiA_own_entry', '')
+call s:record(nuwiki#diary#calendar_sign(10, 6, 2026) ==# '', 'track.wikiA_not_wikiB_entry', '')
+
+call nuwiki#diary#track_wiki(s:wB . '/index.wiki')
+call s:record(nuwiki#diary#calendar_sign(10, 6, 2026) ==# '*', 'track.wikiB_own_entry', '')
+call s:record(nuwiki#diary#calendar_sign(2, 6, 2026) ==# '', 'track.wikiB_not_wikiA_entry', '')
+unlet g:nuwiki_wikis
+
 " ===== Wrap up =====
 
 call add(s:results, '')
diff --git a/plugin/nuwiki.vim b/plugin/nuwiki.vim
index 86e1b51..3b6ca56 100644
--- a/plugin/nuwiki.vim
+++ b/plugin/nuwiki.vim
@@ -37,6 +37,11 @@ endif
 augroup nuwiki_calendar_detect
   autocmd!
   autocmd FileType vimwiki call s:nuwiki_setup_calendar()
+  " Track the wiki of the active buffer so the calendar diaries into the wiki
+  " you're editing (not always the first one). FileType covers initial load;
+  " BufEnter covers switching back to an already-open wiki buffer.
+  autocmd FileType vimwiki call nuwiki#diary#track_wiki(expand('%:p'))
+  autocmd BufEnter * if &filetype ==# 'vimwiki' | call nuwiki#diary#track_wiki(expand('%:p')) | endif
 augroup END
 function! s:nuwiki_setup_calendar() abort
   if !get(g:, 'nuwiki_use_calendar', 1) || get(g:, 'nuwiki_no_calendar', 0)