looks like my attempts to restore from backup may have killed the logs
this is the error log for around that time but there is a massive gap
2015-04-06 15:20:50+0800 [-] [caldav-0] [IMAP4DownloadProtocol (TLSMemoryBIOProtocol),client] [txdav.caldav.datastore.scheduling.imip.inbound.IMAP4DownloadProtocol#error] IMAP login failed for admin
2015-04-06 15:21:21+0800 [-] [caldav-0] [IMAP4DownloadProtocol (TLSMemoryBIOProtocol),client] [txdav.caldav.datastore.scheduling.imip.inbound.IMAP4DownloadProtocol#error] IMAP login failed for admin
2015-04-06 15:21:51+0800 [-] [caldav-0] [IMAP4DownloadProtocol (TLSMemoryBIOProtocol),client] [txdav.caldav.datastore.scheduling.imip.inbound.IMAP4DownloadProtocol#error] IMAP login failed for admin
2015-04-06 15:22:22+0800 [-] [caldav-0] [IMAP4DownloadProtocol (TLSMemoryBIOProtocol),client] [txdav.caldav.datastore.scheduling.imip.inbound.IMAP4DownloadProtocol#error] IMAP login failed for admin
2015-04-06 15:22:53+0800 [-] [caldav-0] [IMAP4DownloadProtocol (TLSMemoryBIOProtocol),client] [txdav.caldav.datastore.scheduling.imip.inbound.IMAP4DownloadProtocol#error] IMAP login failed for admin
2015-04-06 15:23:24+0800 [-] [caldav-0] [IMAP4DownloadProtocol (TLSMemoryBIOProtocol),client] [txdav.caldav.datastore.scheduling.imip.inbound.IMAP4DownloadProtocol#error] IMAP login failed for admin
2015-04-06 15:23:54+0800 [-] [caldav-0] [IMAP4DownloadProtocol (TLSMemoryBIOProtocol),client] [txdav.caldav.datastore.scheduling.imip.inbound.IMAP4DownloadProtocol#error] IMAP login failed for admin
2015-04-06 15:24:25+0800 [-] [caldav-0] [IMAP4DownloadProtocol (TLSMemoryBIOProtocol),client] [txdav.caldav.datastore.scheduling.imip.inbound.IMAP4DownloadProtocol#error] IMAP login failed for admin
2015-04-25 19:44:11+0800 [-] Log opened.
2015-04-25 19:44:11+0800 [-] ControlSocket starting on '/var/run/caldavd/caldavd.sock'
2015-04-25 19:44:12+0800 [-] [txdav.base.datastore.subpostgres#warn] Creating /var/run/caldavd/PostgresSocket
2015-04-25 19:44:12+0800 [-] [txdav.base.datastore.subpostgres#warn] Running initdb for /Library/Server/Calendar and Contacts/Data/Database.xpg/cluster.pg
2015-04-25 19:44:22+0800 [-] [txdav.base.datastore.subpostgres#warn] Requesting postgres start via /Applications/Server.app/Contents/ServerRoot/usr/bin/xpg_ctl ["-c listen_addresses=''", '-k /var/run/caldavd/PostgresSocket', '-c shared_buffers=105', '-c max_connections=70', '-c standard_conforming_strings=on', '-c unix_socket_permissions=0770', '-c log_lock_waits=TRUE', '-c deadlock_timeout=10', "-c log_line_prefix='%m [%p] '", "-c log_directory='/Library/Server/Calendar and Contacts/Logs'", '-c log_truncate_on_rotation=on', '-c log_filename=postgresql_%w.log', '-c log_rotation_age=1440', '-c logging_collector=on']
2015-04-25 19:44:29+0800 [-] [txdav.base.datastore.subpostgres#warn] received postgres stdout "2015-04-25 19:44:29 XPG.503: Spawning... ('/usr/bin/tar', '-xz', '-f', '/Library/Server/Calendar and Contacts/Data/Database.xpg/backup/base_backup/base_complete.tar.gz', '-C', '/Library/Server/Calendar and Contacts/Data/Database.xpg/cluster.pg')\\n"
2015-04-25 19:44:34+0800 [-] [txdav.base.datastore.subpostgres#warn] received postgres stdout '2015-04-25 19:44:34 XPG.503: Waiting for data directory: /Library/Server/Calendar and Contacts/Data/Database.xpg/cluster.pg\\n'
2015-04-25 19:44:34+0800 [-] [txdav.base.datastore.subpostgres#warn] received postgres stdout '2015-04-25 19:44:34 XPG.503: Data directory exists.\\n'
2015-04-25 19:44:34+0800 [-] [txdav.base.datastore.subpostgres#warn] received postgres stdout '2015-04-25 19:44:34 XPG.503: Spawning postgres for restore only.\\n2015-04-25 19:44:34 XPG.503: Spawning postgres now.\\n'
2015-04-25 19:44:34+0800 [-] [txdav.base.datastore.subpostgres#warn] received postgres stdout '2015-04-25 19:44:34 XPG.503: Waiting for recovery done notification.\\n'
2015-04-25 19:44:35+0800 [-] [txdav.base.datastore.subpostgres#warn] received postgres stderr LOG: redirecting log output to logging collector process
HINT: Future log output will appear in directory "/Library/Server/Calendar and Contacts/Logs".