diff --git a/lua/git/blame.lua b/lua/git/blame.lua
index b6cee34..f2ef5d7 100644
--- a/lua/git/blame.lua
+++ b/lua/git/blame.lua
@@ -56,21 +56,6 @@ function M.state(buf)
     return states[buf]
 end
 
----@param ts integer
----@param tz string
----@return string
-local function format_author_time(ts, tz)
-    local sign, hh, mm = tz:match("^([+-])(%d%d)(%d%d)$")
-    ---@type number
-    local offset = 0
-    if sign then
-        local h = tonumber(hh) or 0
-        local m = tonumber(mm) or 0
-        offset = (h * 3600 + m * 60) * (sign == "-" and -1 or 1)
-    end
-    return os.date("!%Y-%m-%d %T ", ts + offset) .. tz
-end
-
 ---@param stdout string
 ---@return ow.Git.Blame.Result
 local function parse_porcelain(stdout)
@@ -534,7 +519,7 @@ local function open_popup(state, lnum, watch_buf)
         head = { "Not Committed Yet" }
     else
         local short = sha:sub(1, 8)
-        local date = format_author_time(commit.author_time, commit.author_tz)
+        local date = util.format_git_time(commit.author_time, commit.author_tz)
         sha_len = #short
         date_col = sha_len + 2 + #commit.author + 2
         head = {
diff --git a/lua/git/core/util.lua b/lua/git/core/util.lua
index 0c85d41..9e956da 100644
--- a/lua/git/core/util.lua
+++ b/lua/git/core/util.lua
@@ -120,6 +120,23 @@ function M.split_lines(content)
     return lines
 end
 
+---@param ts integer
+---@param tz string
+---@return string
+function M.format_git_time(ts, tz)
+    local sign, hh, mm = tz:match("^([+-])(%d%d)(%d%d)$")
+    local offset = 0
+    if sign then
+        local h = tonumber(hh) or 0
+        local m = tonumber(mm) or 0
+        offset = math.floor(h * 3600 + m * 60)
+        if sign == "-" then
+            offset = -offset
+        end
+    end
+    return os.date("!%a %b %e %T %Y ", ts + offset) .. tz
+end
+
 ---@param buf integer
 ---@param ns integer
 ---@param lines string[]
diff --git a/lua/git/object.lua b/lua/git/object.lua
index 8898832..d0619ce 100644
--- a/lua/git/object.lua
+++ b/lua/git/object.lua
@@ -159,6 +159,29 @@ function M.buf_for(r, rev)
     return buf
 end
 
+---@param lines string[]
+local function format_header_dates(lines)
+    for i, line in ipairs(lines) do
+        if line == "" then
+            return
+        end
+        local prefix, ts, tz = line:match("^(author .-) (%d+) ([+-]%d%d%d%d)$")
+        if not prefix then
+            prefix, ts, tz = line:match("^(committer .-) (%d+) ([+-]%d%d%d%d)$")
+        end
+        if not prefix then
+            prefix, ts, tz = line:match("^(tagger .-) (%d+) ([+-]%d%d%d%d)$")
+        end
+        if prefix then
+            local n = math.floor(assert(tonumber(ts)))
+            lines[i] = ("%s %s"):format(
+                prefix,
+                util.format_git_time(n, tz --[[@as string]])
+            )
+        end
+    end
+end
+
 ---@param buf integer
 ---@param r ow.Git.Repo
 ---@param rev ow.Git.Revision
@@ -189,7 +212,9 @@ local function populate(buf, r, rev, state, rev_sha)
         end
     end
 
-    util.set_buf_lines(buf, 0, -1, util.split_lines(stdout))
+    local lines = util.split_lines(stdout)
+    format_header_dates(lines)
+    util.set_buf_lines(buf, 0, -1, lines)
     state.sha = rev_sha
     return true
 end
diff --git a/test/git/blame_test.lua b/test/git/blame_test.lua
index e031f65..ce8f404 100644
--- a/test/git/blame_test.lua
+++ b/test/git/blame_test.lua
@@ -86,9 +86,9 @@ t.test("line popup formats the datetime in the author timezone", function()
     )
     t.truthy(
         (lines[1] or ""):match(
-            "%d%d%d%d%-%d%d%-%d%d %d%d:%d%d:%d%d [+%-]%d%d%d%d$"
+            "%u%l%l %u%l%l +%d+ %d%d:%d%d:%d%d %d%d%d%d [+%-]%d%d%d%d$"
         ),
-        "the head line ends with an ISO datetime and numeric timezone"
+        "the head line ends with a human datetime and numeric timezone"
     )
 end)
 
diff --git a/test/git/object_test.lua b/test/git/object_test.lua
index 0082d21..b90f9ee 100644
--- a/test/git/object_test.lua
+++ b/test/git/object_test.lua
@@ -134,6 +134,45 @@ t.test("read_uri opens stage-0 entry as a writable index buffer", function()
     t.eq(vim.api.nvim_buf_get_lines(buf, 0, -1, false), { "first" })
 end)
 
+t.test("M.open renders author/committer dates, not unix timestamps", function()
+    local dir = h.make_repo({ a = "first\n" })
+    local r = assert(require("git.core.repo").resolve(dir))
+
+    object.open(r, "HEAD", { split = false })
+    local author = assert(find_line(0, "author "), "expected an author line")
+    local committer =
+        assert(find_line(0, "committer "), "expected a committer line")
+    local lines = vim.api.nvim_buf_get_lines(0, 0, -1, false)
+    for _, lnum in ipairs({ author, committer }) do
+        local line = assert(lines[lnum])
+        t.truthy(
+            line:match(
+                " %u%l%l %u%l%l +%d+ %d%d:%d%d:%d%d %d%d%d%d [+-]%d%d%d%d$"
+            ),
+            "expected formatted date on: " .. line
+        )
+        t.falsy(
+            line:match(" %d%d%d%d%d%d%d%d%d%d? [+-]%d%d%d%d$"),
+            "expected no unix timestamp on: " .. line
+        )
+    end
+end)
+
+t.test("M.open renders tagger dates on annotated tags", function()
+    local dir = h.make_repo({ a = "first\n" })
+    h.git(dir, "tag", "-m", "rel", "v1")
+    local r = assert(require("git.core.repo").resolve(dir))
+
+    object.open(r, "v1", { split = false })
+    local tagger = assert(find_line(0, "tagger "), "expected a tagger line")
+    local line =
+        assert(vim.api.nvim_buf_get_lines(0, tagger - 1, tagger, false)[1])
+    t.truthy(
+        line:match(" %u%l%l %u%l%l +%d+ %d%d:%d%d:%d%d %d%d%d%d [+-]%d%d%d%d$"),
+        "expected formatted date on: " .. line
+    )
+end)
+
 t.test("open_under_cursor on a 'tree <sha>' line opens the tree", function()
     local dir = h.make_repo({ a = "first\n" })
     local r = assert(require("git.core.repo").resolve(dir))